GCC 4.7.4 toolchain Beta 2

Mingw64 GCC 32 bit toolchain using version 4.7.4 (git 4.7 branch with patches)

Install the support packages and then the toolchain packages.
The packages are for the MSys2 MINGW32 environment and are installed to /opt/mingw32 folder.

See "GCC 4.9.4 toolchain Alpha 3" for MINGW64 64 bit packages.