...
The GNU toolchain is the only major C/C++ toolchain with limited support of Windows on Arm64 target. Clang/LLVM and MSVC already have a solid support.
Many downstream open-source toolchains, such as MinGW, Cygwin, and MSYS2 expressed interested in supporting WoARM64 if GCC was available.
The Arm64 porting is happening at https://github.com/Windows-on-ARM-Experiments/mingw-woarm64-build
...