Add a note about requiring Xcode for ios development
Add a note about requiring Xcode for ios development

Summary: Closes https://github.com/facebook/buck/pull/1113

Reviewed By: Coneko, JoelMarcey

fbshipit-source-id: 8846214

shybovycha/buck,facebook/buck,shs96c/buck,darkforestzero/buck,rmaz/buck,romanoid/buck,sdwilsh/buck,clonetwin26/buck,shs96c/buck,shybovycha/buck,JoelMarcey/buck,sdwilsh/buck,sdwilsh/buck,SeleniumHQ/buck,daedric/buck,marcinkwiatkowski/buck,LegNeato/buck,daedric/buck,nguyentruongtho/buck,vschs007/buck,k21/buck,clonetwin26/buck,shs96c/buck,shs96c/buck,LegNeato/buck,vschs007/buck,JoelMarcey/buck,davido/buck,vschs007/buck,rmaz/buck,k21/buck,k21/buck,sdwilsh/buck,shybovycha/buck,ilya-klyuchnikov/buck,clonetwin26/buck,grumpyjames/buck,vschs007/buck,marcinkwiatkowski/buck,marcinkwiatkowski/buck,zhan-xiong/buck,ilya-klyuchnikov/buck,romanoid/buck,clonetwin26/buck,robbertvanginkel/buck,rmaz/buck,davido/buck,dsyang/buck,robbertvanginkel/buck,robbertvanginkel/buck,grumpyjames/buck,robbertvanginkel/buck,romanoid/buck,k21/buck,darkforestzero/buck,ilya-klyuchnikov/buck,marcinkwiatkowski/buck,shs96c/buck,romanoid/buck,ilya-klyuchnikov/buck,zhan-xiong/buck,kageiit/buck,zhan-xiong/buck,LegNeato/buck,clonetwin26/buck,rmaz/buck,sdwilsh/buck,darkforestzero/buck,davido/buck,nguyentruongtho/buck,robbertvanginkel/buck,rmaz/buck,daedric/buck,kageiit/buck,kageiit/buck,JoelMarcey/buck,grumpyjames/buck,vschs007/buck,ilya-klyuchnikov/buck,brettwooldridge/buck,grumpyjames/buck,romanoid/buck,zpao/buck,shybovycha/buck,davido/buck,davido/buck,zhan-xiong/buck,k21/buck,sdwilsh/buck,SeleniumHQ/buck,marcinkwiatkowski/buck,daedric/buck,dsyang/buck,vschs007/buck,marcinkwiatkowski/buck,brettwooldridge/buck,dsyang/buck,shybovycha/buck,robbertvanginkel/buck,shs96c/buck,daedric/buck,facebook/buck,darkforestzero/buck,clonetwin26/buck,robbertvanginkel/buck,JoelMarcey/buck,romanoid/buck,dsyang/buck,davido/buck,Addepar/buck,shybovycha/buck,zpao/buck,kageiit/buck,kageiit/buck,JoelMarcey/buck,ilya-klyuchnikov/buck,Addepar/buck,vschs007/buck,daedric/buck,darkforestzero/buck,davido/buck,dsyang/buck,nguyentruongtho/buck,rmaz/buck,LegNeato/buck,zhan-xiong/buck,Addepar/buck,darkforestzero/buck,kageiit/buck,daedric/buck,marcinkwiatkowski/buck,JoelMarcey/buck,davido/buck,facebook/buck,vschs007/buck,marcinkwiatkowski/buck,robbertvanginkel/buck,LegNeato/buck,SeleniumHQ/buck,dsyang/buck,k21/buck,daedric/buck,daedric/buck,JoelMarcey/buck,brettwooldridge/buck,JoelMarcey/buck,shybovycha/buck,dsyang/buck,romanoid/buck,davido/buck,sdwilsh/buck,JoelMarcey/buck,clonetwin26/buck,robbertvanginkel/buck,shybovycha/buck,JoelMarcey/buck,sdwilsh/buck,zhan-xiong/buck,daedric/buck,vschs007/buck,Addepar/buck,zhan-xiong/buck,sdwilsh/buck,dsyang/buck,zpao/buck,Addepar/buck,brettwooldridge/buck,facebook/buck,brettwooldridge/buck,rmaz/buck,shs96c/buck,shybovycha/buck,kageiit/buck,rmaz/buck,nguyentruongtho/buck,dsyang/buck,brettwooldridge/buck,robbertvanginkel/buck,grumpyjames/buck,shybovycha/buck,grumpyjames/buck,darkforestzero/buck,grumpyjames/buck,clonetwin26/buck,darkforestzero/buck,shs96c/buck,zpao/buck,clonetwin26/buck,LegNeato/buck,davido/buck,LegNeato/buck,LegNeato/buck,ilya-klyuchnikov/buck,Addepar/buck,k21/buck,robbertvanginkel/buck,romanoid/buck,vschs007/buck,romanoid/buck,davido/buck,zpao/buck,JoelMarcey/buck,SeleniumHQ/buck,grumpyjames/buck,k21/buck,darkforestzero/buck,zhan-xiong/buck,Addepar/buck,LegNeato/buck,dsyang/buck,daedric/buck,sdwilsh/buck,clonetwin26/buck,clonetwin26/buck,rmaz/buck,marcinkwiatkowski/buck,marcinkwiatkowski/buck,Addepar/buck,SeleniumHQ/buck,LegNeato/buck,Addepar/buck,grumpyjames/buck,vschs007/buck,zhan-xiong/buck,facebook/buck,Addepar/buck,Addepar/buck,vschs007/buck,nguyentruongtho/buck,ilya-klyuchnikov/buck,rmaz/buck,ilya-klyuchnikov/buck,sdwilsh/buck,brettwooldridge/buck,darkforestzero/buck,rmaz/buck,k21/buck,SeleniumHQ/buck,ilya-klyuchnikov/buck,daedric/buck,robbertvanginkel/buck,Addepar/buck,k21/buck,LegNeato/buck,Addepar/buck,SeleniumHQ/buck,LegNeato/buck,sdwilsh/buck,dsyang/buck,romanoid/buck,darkforestzero/buck,shybovycha/buck,brettwooldridge/buck,marcinkwiatkowski/buck,romanoid/buck,SeleniumHQ/buck,clonetwin26/buck,shs96c/buck,SeleniumHQ/buck,marcinkwiatkowski/buck,romanoid/buck,nguyentruongtho/buck,zhan-xiong/buck,SeleniumHQ/buck,marcinkwiatkowski/buck,robbertvanginkel/buck,ilya-klyuchnikov/buck,daedric/buck,darkforestzero/buck,SeleniumHQ/buck,shybovycha/buck,shs96c/buck,shs96c/buck,zhan-xiong/buck,shybovycha/buck,brettwooldridge/buck,k21/buck,brettwooldridge/buck,zhan-xiong/buck,k21/buck,facebook/buck,dsyang/buck,LegNeato/buck,dsyang/buck,ilya-klyuchnikov/buck,davido/buck,rmaz/buck,nguyentruongtho/buck,zpao/buck,grumpyjames/buck,grumpyjames/buck,JoelMarcey/buck,clonetwin26/buck,k21/buck,shs96c/buck,facebook/buck,davido/buck,brettwooldridge/buck,SeleniumHQ/buck,ilya-klyuchnikov/buck,romanoid/buck,zhan-xiong/buck,sdwilsh/buck,rmaz/buck,zpao/buck,grumpyjames/buck,darkforestzero/buck,JoelMarcey/buck,SeleniumHQ/buck,vschs007/buck,shs96c/buck,brettwooldridge/buck,brettwooldridge/buck