Make fails on 10.9.4 due to no gcc (clang only)

[fherbert]

Running CC=gcc-4.2 make install-cross fails on my Mavericks build with errors about redefinitions of functions is not supported in C99 mode.
This is due to clang defaulting to C99 mode when building, and Mavericks doesn't come with gcc any more - it's all clang now:
gcc --version
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
Target: x86_64-apple-darwin13.3.0
Thread model: posix

So to fix this, I ran make with the following parameters:
CC='gcc-4.2 -std=gnu89' make install-cross