simplify and comment build_location/correct_build_location
simplify and comment build_location/correct_build_location

- add a bunch of comments
- renamed correct_build_location to _correct_build_location
- use build_location inside of _correct_build_location to be consistent
  with the other build directories

supriyantomaftuh/pip,alex/pip,h4ck3rm1k3/pip,jmagnusson/pip,jythontools/pip,Gabriel439/pip,jythontools/pip,habnabit/pip,mindw/pip,natefoo/pip,pypa/pip,rbtcollins/pip,fiber-space/pip,yati-sagade/pip,rouge8/pip,prasaianooz/pip,ChristopherHogan/pip,jythontools/pip,harrisonfeng/pip,zvezdan/pip,erikrose/pip,zorosteven/pip,mujiansu/pip,pradyunsg/pip,jmagnusson/pip,sbidoul/pip,blarghmatey/pip,qbdsoft/pip,atdaemon/pip,Gabriel439/pip,benesch/pip,zenlambda/pip,harrisonfeng/pip,dstufft/pip,tdsmith/pip,h4ck3rm1k3/pip,habnabit/pip,zvezdan/pip,haridsv/pip,harrisonfeng/pip,prasaianooz/pip,graingert/pip,davidovich/pip,mindw/pip,blarghmatey/pip,haridsv/pip,caosmo/pip,graingert/pip,James-Firth/pip,yati-sagade/pip,jamezpolley/pip,ncoghlan/pip,rouge8/pip,dstufft/pip,James-Firth/pip,davidovich/pip,luzfcb/pip,supriyantomaftuh/pip,pfmoore/pip,willingc/pip,qbdsoft/pip,willingc/pip,chaoallsome/pip,pfmoore/pip,benesch/pip,qbdsoft/pip,sigmavirus24/pip,erikrose/pip,KarelJakubec/pip,mujiansu/pip,nthall/pip,squidsoup/pip,jasonkying/pip,squidsoup/pip,fiber-space/pip,jasonkying/pip,chaoallsome/pip,KarelJakubec/pip,ChristopherHogan/pip,dstufft/pip,jamezpolley/pip,rbtcollins/pip,esc/pip,xavfernandez/pip,KarelJakubec/pip,sigmavirus24/pip,techtonik/pip,xavfernandez/pip,esc/pip,atdaemon/pip,jmagnusson/pip,esc/pip,pradyunsg/pip,squidsoup/pip,graingert/pip,James-Firth/pip,mujiansu/pip,prasaianooz/pip,supriyantomaftuh/pip,nthall/pip,RonnyPfannschmidt/pip,natefoo/pip,caosmo/pip,atdaemon/pip,nthall/pip,davidovich/pip,chaoallsome/pip,h4ck3rm1k3/pip,yati-sagade/pip,natefoo/pip,wkeyword/pip,techtonik/pip,pypa/pip,ChristopherHogan/pip,wkeyword/pip,tdsmith/pip,erikrose/pip,wkeyword/pip,benesch/pip,jamezpolley/pip,zorosteven/pip,haridsv/pip,rouge8/pip,blarghmatey/pip,techtonik/pip,fiber-space/pip,sigmavirus24/pip,ncoghlan/pip,alex/pip,habnabit/pip,mindw/pip,willingc/pip,sbidoul/pip,ncoghlan/pip,zvezdan/pip,alex/pip,luzfcb/pip,tdsmith/pip,xavfernandez/pip,rbtcollins/pip,RonnyPfannschmidt/pip,zorosteven/pip,zenlambda/pip,RonnyPfannschmidt/pip,jasonkying/pip,zenlambda/pip,caosmo/pip,Gabriel439/pip,luzfcb/pip