Fix a bug in Genrule: order of srcs matters.
Fix a bug in Genrule: order of srcs matters.

Summary:
The order of `this.srcs` matters because it affects
the creation of the `$SRCS` environment variable when
executing the genrule. Users should be able to depend
on this order.

Test Plan: Sandcastle builds.

siddhartharay007/buck,shybovycha/buck,davido/buck,zhuxiaohao/buck,justinmuller/buck,SeleniumHQ/buck,facebook/buck,denizt/buck,robbertvanginkel/buck,Addepar/buck,raviagarwal7/buck,MarkRunWu/buck,kageiit/buck,lukw00/buck,jackminicloud/buck,kageiit/buck,dsyang/buck,clonetwin26/buck,robbertvanginkel/buck,daedric/buck,artiya4u/buck,raviagarwal7/buck,hgl888/buck,daedric/buck,tgummerer/buck,tgummerer/buck,vschs007/buck,tgummerer/buck,OkBuilds/buck,daedric/buck,romanoid/buck,vine/buck,brettwooldridge/buck,OkBuilds/buck,shybovycha/buck,Dominator008/buck,bocon13/buck,daedric/buck,darkforestzero/buck,pwz3n0/buck,JoelMarcey/buck,illicitonion/buck,dushmis/buck,rowillia/buck,shs96c/buck,daedric/buck,illicitonion/buck,SeleniumHQ/buck,mnuessler/buck,rhencke/buck,zpao/buck,bocon13/buck,robbertvanginkel/buck,dpursehouse/buck,tgummerer/buck,romanoid/buck,LegNeato/buck,ilya-klyuchnikov/buck,dushmis/buck,dpursehouse/buck,mikekap/buck,brettwooldridge/buck,shs96c/buck,ilya-klyuchnikov/buck,SeleniumHQ/buck,dsyang/buck,shybovycha/buck,nguyentruongtho/buck,kageiit/buck,Dominator008/buck,vine/buck,vine/buck,OkBuilds/buck,ilya-klyuchnikov/buck,Heart2009/buck,sdwilsh/buck,liuyang-li/buck,janicduplessis/buck,nguyentruongtho/buck,dushmis/buck,vschs007/buck,Distrotech/buck,OkBuilds/buck,marcinkwiatkowski/buck,sdwilsh/buck,mogers/buck,vschs007/buck,rhencke/buck,zpao/buck,k21/buck,dushmis/buck,sdwilsh/buck,rmaz/buck,darkforestzero/buck,marcinkwiatkowski/buck,MarkRunWu/buck,justinmuller/buck,dushmis/buck,justinmuller/buck,SeleniumHQ/buck,Dominator008/buck,liuyang-li/buck,belomx/open_tools,1yvT0s/buck,clonetwin26/buck,shybovycha/buck,SeleniumHQ/buck,darkforestzero/buck,OkBuilds/buck,siddhartharay007/buck,artiya4u/buck,rmaz/buck,lukw00/buck,tgummerer/buck,1yvT0s/buck,LegNeato/buck,dsyang/buck,marcinkwiatkowski/buck,nguyentruongtho/buck,Heart2009/buck,vschs007/buck,Learn-Android-app/buck,mnuessler/buck,Dominator008/buck,rowillia/buck,dsyang/buck,facebook/buck,rhencke/buck,thinkernel/buck,shybovycha/buck,pwz3n0/buck,Heart2009/buck,sdwilsh/buck,dushmis/buck,jackminicloud/buck,Heart2009/buck,zhan-xiong/buck,tgummerer/buck,grumpyjames/buck,Addepar/buck,bocon13/buck,liuyang-li/buck,raviagarwal7/buck,mread/buck,siddhartharay007/buck,stuhood/buck,Dominator008/buck,ilya-klyuchnikov/buck,darkforestzero/buck,luiseduardohdbackup/buck,Dominator008/buck,stuhood/buck,justinmuller/buck,Dominator008/buck,k21/buck,shybovycha/buck,luiseduardohdbackup/buck,ilya-klyuchnikov/buck,k21/buck,LegNeato/buck,LegNeato/buck,davido/buck,shs96c/buck,darkforestzero/buck,shybovycha/buck,hgl888/buck,mogers/buck,daedric/buck,clonetwin26/buck,janicduplessis/buck,brettwooldridge/buck,romanoid/buck,mikekap/buck,mread/buck,rmaz/buck,davido/buck,rowillia/buck,mogers/buck,nguyentruongtho/buck,mnuessler/buck,zpao/buck,MarkRunWu/buck,OkBuilds/buck,vine/buck,zhan-xiong/buck,neonichu/buck,artiya4u/buck,1yvT0s/buck,shybovycha/buck,stuhood/buck,grumpyjames/buck,shs96c/buck,liuyang-li/buck,nguyentruongtho/buck,vschs007/buck,neonichu/buck,marcinkwiatkowski/buck,Dominator008/buck,Addepar/buck,justinmuller/buck,mread/buck,illicitonion/buck,Learn-Android-app/buck,liuyang-li/buck,belomx/open_tools,liuyang-li/buck,zhuxiaohao/buck,zhan-xiong/buck,grumpyjames/buck,grumpyjames/buck,janicduplessis/buck,marcinkwiatkowski/buck,brettwooldridge/buck,saleeh93/buck-cutom,liuyang-li/buck,saleeh93/buck-cutom,mogers/buck,mikekap/buck,darkforestzero/buck,daedric/buck,romanoid/buck,pwz3n0/buck,pwz3n0/buck,shs96c/buck,neonichu/buck,Addepar/buck,pwz3n0/buck,robbertvanginkel/buck,Learn-Android-app/buck,mikekap/buck,dpursehouse/buck,brettwooldridge/buck,artiya4u/buck,Learn-Android-app/buck,dpursehouse/buck,mikekap/buck,shs96c/buck,shs96c/buck,romanoid/buck,shs96c/buck,k21/buck,Distrotech/buck,Dominator008/buck,clonetwin26/buck,davido/buck,Heart2009/buck,rmaz/buck,mikekap/buck,JoelMarcey/buck,janicduplessis/buck,rmaz/buck,saleeh93/buck-cutom,illicitonion/buck,tgummerer/buck,ilya-klyuchnikov/buck,stuhood/buck,justinmuller/buck,Learn-Android-app/buck,rmaz/buck,romanoid/buck,justinmuller/buck,darkforestzero/buck,mikekap/buck,mogers/buck,Learn-Android-app/buck,justinmuller/buck,dsyang/buck,OkBuilds/buck,pwz3n0/buck,ilya-klyuchnikov/buck,MarkRunWu/buck,zpao/buck,raviagarwal7/buck,dsyang/buck,zhan-xiong/buck,zpao/buck,luiseduardohdbackup/buck,Addepar/buck,tgummerer/buck,nguyentruongtho/buck,neonichu/buck,Addepar/buck,ilya-klyuchnikov/buck,saleeh93/buck-cutom,marcinkwiatkowski/buck,lukw00/buck,illicitonion/buck,sdwilsh/buck,zhan-xiong/buck,romanoid/buck,shybovycha/buck,rowillia/buck,sdwilsh/buck,clonetwin26/buck,grumpyjames/buck,dsyang/buck,daedric/buck,vschs007/buck,k21/buck,saleeh93/buck-cutom,mnuessler/buck,luiseduardohdbackup/buck,Distrotech/buck,neonichu/buck,siddhartharay007/buck,dpursehouse/buck,k21/buck,mikekap/buck,clonetwin26/buck,romanoid/buck,1yvT0s/buck,JoelMarcey/buck,LegNeato/buck,luiseduardohdbackup/buck,bocon13/buck,stuhood/buck,k21/buck,neonichu/buck,justinmuller/buck,hgl888/buck,illicitonion/buck,artiya4u/buck,dsyang/buck,marcinkwiatkowski/buck,clonetwin26/buck,lukw00/buck,daedric/buck,sdwilsh/buck,Learn-Android-app/buck,Dominator008/buck,darkforestzero/buck,facebook/buck,rmaz/buck,marcinkwiatkowski/buck,mread/buck,justinmuller/buck,bocon13/buck,facebook/buck,rmaz/buck,kageiit/buck,shs96c/buck,zhuxiaohao/buck,LegNeato/buck,davido/buck,artiya4u/buck,rowillia/buck,romanoid/buck,lukw00/buck,JoelMarcey/buck,darkforestzero/buck,vine/buck,mikekap/buck,zhan-xiong/buck,liuyang-li/buck,Dominator008/buck,siddhartharay007/buck,janicduplessis/buck,JoelMarcey/buck,nguyentruongtho/buck,neonichu/buck,sdwilsh/buck,JoelMarcey/buck,JoelMarcey/buck,LegNeato/buck,dushmis/buck,JoelMarcey/buck,mnuessler/buck,zhuxiaohao/buck,thinkernel/buck,davido/buck,rowillia/buck,rhencke/buck,zpao/buck,janicduplessis/buck,rhencke/buck,zhuxiaohao/buck,romanoid/buck,SeleniumHQ/buck,davido/buck,hgl888/buck,luiseduardohdbackup/buck,jackminicloud/buck,ilya-klyuchnikov/buck,vschs007/buck,illicitonion/buck,vine/buck,rhencke/buck,Addepar/buck,JoelMarcey/buck,SeleniumHQ/buck,robbertvanginkel/buck,romanoid/buck,mnuessler/buck,vschs007/buck,hgl888/buck,dpursehouse/buck,dsyang/buck,stuhood/buck,shs96c/buck,mnuessler/buck,robbertvanginkel/buck,stuhood/buck,tgummerer/buck,justinmuller/buck,zpao/buck,raviagarwal7/buck,mread/buck,shybovycha/buck,hgl888/buck,clonetwin26/buck,vschs007/buck,daedric/buck,daedric/buck,brettwooldridge/buck,raviagarwal7/buck,vschs007/buck,bocon13/buck,robbertvanginkel/buck,brettwooldridge/buck,vine/buck,neonichu/buck,stuhood/buck,rhencke/buck,SeleniumHQ/buck,Distrotech/buck,shybovycha/buck,dpursehouse/buck,SeleniumHQ/buck,hgl888/buck,denizt/buck,zhuxiaohao/buck,Distrotech/buck,justinmuller/buck,vine/buck,sdwilsh/buck,brettwooldridge/buck,k21/buck,kageiit/buck,Dominator008/buck,clonetwin26/buck,artiya4u/buck,vine/buck,davido/buck,robbertvanginkel/buck,Addepar/buck,illicitonion/buck,vschs007/buck,LegNeato/buck,GerritCodeReview/buck,LegNeato/buck,grumpyjames/buck,davido/buck,liuyang-li/buck,illicitonion/buck,LegNeato/buck,rmaz/buck,robbertvanginkel/buck,ilya-klyuchnikov/buck,Heart2009/buck,OkBuilds/buck,robbertvanginkel/buck,raviagarwal7/buck,Heart2009/buck,zhan-xiong/buck,SeleniumHQ/buck,marcinkwiatkowski/buck,justinmuller/buck,MarkRunWu/buck,liuyang-li/buck,denizt/buck,mogers/buck,Addepar/buck,Addepar/buck,illicitonion/buck,siddhartharay007/buck,hgl888/buck,denizt/buck,davido/buck,pwz3n0/buck,pwz3n0/buck,dushmis/buck,k21/buck,Learn-Android-app/buck,daedric/buck,janicduplessis/buck,rhencke/buck,grumpyjames/buck,artiya4u/buck,bocon13/buck,pwz3n0/buck,SeleniumHQ/buck,darkforestzero/buck,romanoid/buck,rowillia/buck,brettwooldridge/buck,k21/buck,siddhartharay007/buck,neonichu/buck,rowillia/buck,zhan-xiong/buck,thinkernel/buck,brettwooldridge/buck,luiseduardohdbackup/buck,kageiit/buck,mogers/buck,belomx/open_tools,denizt/buck,shybovycha/buck,raviagarwal7/buck,1yvT0s/buck,lukw00/buck,Distrotech/buck,shs96c/buck,zhan-xiong/buck,vschs007/buck,grumpyjames/buck,zhuxiaohao/buck,stuhood/buck,k21/buck,saleeh93/buck-cutom,hgl888/buck,lukw00/buck,GerritCodeReview/buck,shybovycha/buck,1yvT0s/buck,Distrotech/buck,Distrotech/buck,davido/buck,shs96c/buck,stuhood/buck,luiseduardohdbackup/buck,illicitonion/buck,sdwilsh/buck,bocon13/buck,SeleniumHQ/buck,illicitonion/buck,davido/buck,darkforestzero/buck,janicduplessis/buck,Distrotech/buck,grumpyjames/buck,facebook/buck,dushmis/buck,lukw00/buck,darkforestzero/buck,zhan-xiong/buck,1yvT0s/buck,mikekap/buck,bocon13/buck,lukw00/buck,romanoid/buck,dpursehouse/buck,marcinkwiatkowski/buck,zhan-xiong/buck,zhuxiaohao/buck,MarkRunWu/buck,lukw00/buck,pwz3n0/buck,LegNeato/buck,ilya-klyuchnikov/buck,robbertvanginkel/buck,Addepar/buck,OkBuilds/buck,clonetwin26/buck,LegNeato/buck,raviagarwal7/buck,JoelMarcey/buck,1yvT0s/buck,brettwooldridge/buck,OkBuilds/buck,Learn-Android-app/buck,rowillia/buck,stuhood/buck,ilya-klyuchnikov/buck,belomx/open_tools,MarkRunWu/buck,robbertvanginkel/buck,janicduplessis/buck,GerritCodeReview/buck,raviagarwal7/buck,raviagarwal7/buck,artiya4u/buck,Heart2009/buck,clonetwin26/buck,rmaz/buck,Addepar/buck,lukw00/buck,1yvT0s/buck,SeleniumHQ/buck,mogers/buck,grumpyjames/buck,vine/buck,davido/buck,marcinkwiatkowski/buck,liuyang-li/buck,MarkRunWu/buck,rhencke/buck,dsyang/buck,Heart2009/buck,shs96c/buck,facebook/buck,artiya4u/buck,mread/buck,darkforestzero/buck,Learn-Android-app/buck,robbertvanginkel/buck,raviagarwal7/buck,thinkernel/buck,mogers/buck,janicduplessis/buck,rmaz/buck,sdwilsh/buck,zhan-xiong/buck,bocon13/buck,marcinkwiatkowski/buck,vine/buck,zhuxiaohao/buck,janicduplessis/buck,tgummerer/buck,GerritCodeReview/buck,daedric/buck,jackminicloud/buck,mogers/buck,grumpyjames/buck,rowillia/buck,k21/buck,dsyang/buck,rmaz/buck,bocon13/buck,luiseduardohdbackup/buck,OkBuilds/buck,mikekap/buck,zhan-xiong/buck,JoelMarcey/buck,mogers/buck,rhencke/buck,rmaz/buck,pwz3n0/buck,brettwooldridge/buck,Distrotech/buck,clonetwin26/buck,rhencke/buck,artiya4u/buck,grumpyjames/buck,illicitonion/buck,siddhartharay007/buck,rowillia/buck,tgummerer/buck,OkBuilds/buck,clonetwin26/buck,siddhartharay007/buck,Learn-Android-app/buck,raviagarwal7/buck,JoelMarcey/buck,rowillia/buck,mnuessler/buck,facebook/buck,sdwilsh/buck,bocon13/buck,LegNeato/buck,k21/buck,Distrotech/buck,dushmis/buck,dsyang/buck,dsyang/buck,OkBuilds/buck,kageiit/buck,janicduplessis/buck,sdwilsh/buck,brettwooldridge/buck,ilya-klyuchnikov/buck,marcinkwiatkowski/buck,JoelMarcey/buck,Addepar/buck,mikekap/buck,mnuessler/buck,vschs007/buck