Add Windows ARM64 MinGW build support

[driver1998]

Tested in Clang 15/MinGW, on MSYS2 clangarm64 environment.

Two minor workarounds not in this PR are needed for a successful build:

• Convert embree.rc from UTF-16LE to UTF-8 since llvm-rc doesn't seem to support UTF16-LE for some reason.
• Move #define _USE_MATH_DEFINES to the very first time math.h is included, or just add -D_USE_MATH_DEFINES to cflags, because MinGW's math.h does not check _USE_MATH_DEFINES on subsequent includes.

I didn't include them in the PR because I think they are ugly hacks and we should figure out a cleaner way.

[driver1998]

Looks like this is pretty much the same as https://github.com/embree/embree/pull/412. Close this PR then.