Add MinGW cross compiler toolchain
Add MinGW cross compiler toolchain

To enable CI cross compiling, the toolchain works with MinGW-w64

Pireax/neovim-qt,ngkaho1234/neovim-qt,0x90sled/neovim-qt,equalsraf/neovim-qt,0x90sled/neovim-qt,Pireax/neovim-qt,ravloony/neovim-qt,ngkaho1234/neovim-qt,ravloony/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt,0x90sled/neovim-qt,equalsraf/neovim-qt,Pireax/neovim-qt,ngkaho1234/neovim-qt,ravloony/neovim-qt