Use our prebuilt Mingw64 toolchain to build Win32 binaries.

This patch switches the build to always use our custom prebuilt
toolchain (based on GCC 4.8.3 these days) to build our Windows
binaries on Linux.

Note that this still only builds Win32 binaries only, support for
Win64 will appear in a future patch.

Change-Id: I1f7693550518c2c8a5a3ab7fe15261b9bebe61a0
1 file changed