[hack] Allow specifyign hackc compiler id with C define
[hack] Allow specifyign hackc compiler id with C define

Summary:
OSS friendliness:
 - on mac, we *can't* add an ELF section after the fact, we must have it when building
 - script is fb-specific for now (though doens't need to be)

Depends on D6237249

Reviewed By: paulbiss

Differential Revision: D6238694

fbshipit-source-id: 9b07cadb68c7d34e05bdb7094ee23bcf35ae6f4b

ylu1317/flow,facebook/flow,nmote/flow,popham/flow,nmote/flow,mroch/flow,nmote/flow,gabelevi/flow,mroch/flow,JonathanUsername/flow,gabelevi/flow,popham/flow,gabelevi/flow,TiddoLangerak/flow,popham/flow,samwgoldman/flow,facebook/flow,mroch/flow,samwgoldman/flow,TiddoLangerak/flow,claudiopro/flow,jamesgpearce/flow,mroch/flow,JonathanUsername/flow,AgentME/flow,facebook/flow,claudiopro/flow,ylu1317/flow,JonathanUsername/flow,ylu1317/flow,facebook/flow,popham/flow,gabelevi/flow,nmote/flow,JonathanUsername/flow,ylu1317/flow,JonathanUsername/flow,claudiopro/flow,AgentME/flow,claudiopro/flow,TiddoLangerak/flow,facebook/flow,jamesgpearce/flow,TiddoLangerak/flow,JonathanUsername/flow,jamesgpearce/flow,AgentME/flow,samwgoldman/flow,mroch/flow,nmote/flow,samwgoldman/flow,jamesgpearce/flow,popham/flow,TiddoLangerak/flow,AgentME/flow,jamesgpearce/flow,nmote/flow,popham/flow,JonathanUsername/flow,gabelevi/flow,popham/flow,samwgoldman/flow,mroch/flow,facebook/flow,jamesgpearce/flow,nmote/flow,gabelevi/flow,samwgoldman/flow,mroch/flow,jamesgpearce/flow,claudiopro/flow,samwgoldman/flow,ylu1317/flow,AgentME/flow,gabelevi/flow,facebook/flow