C module: Remove -fPIC from the MinGW shared library flags
C module: Move MinGW linker flags into a response file
MinGW: Use g++ as the linker instead of gcc
C module: Set MINGW variable when using the MinGW compiler
c/openssl module: Support MinGW link libraries
Tests: Fix the filecache_luamd5callback test
c/wxwidgets: Add MinGW support