[Bug target/57753] FSF gcc bootstrap needs to use xcrun to bootstrap post-darwin12

[howarth at nitro dot med.uc.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57753

--- Comment #2 from Jack Howarth <howarth at nitro dot med.uc.edu> ---
Okay, the bootstrap without headers outside of the SDK can be simplified on
darwin to…

./configure -with-native-system-header-dir=`xcrun --show-sdk-path`/usr/include
CXX_FOR_BUILD="xcrun g++" CC_FOR_BUILD="xcrun gcc" CXXFLAGS="-O2 -g -iframework
`xcrun --show-sdk-path`/System/Library/Frameworks"