[Bug target/57792] toplevel configure should enable "--with-sysroot="`xcrun --show-sdk-path`"" for darwin13 and later

[howarth at bromo dot med.uc.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57792

--- Comment #11 from howarth at bromo dot med.uc.edu ---
(In reply to Hin-Tak Leung from comment #9)
> Did the change make it into 4.9.2? I recently tried that
> and found that I need the explicit --sysroot:
> https://gcc.gnu.org/ml/gcc-testresults/2014-11/msg00268.html
> 

Also, if you can't find /usr/include on OS X, that means you need to install
the Command Line Tools with 'xcode-select --install'.