Move expensive map computation outside of a loop.
Move expensive map computation outside of a loop.

Summary:
The `sourceTargetToTestNodes` map is the same for all workspaces and it used to
be computed in each iteration of the loop. Move its computation outside of the
loop.

Test Plan: `buck test --all`, generating and compiling an Xcode project.

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