Make ASM_CORE, ASM_SCALERS and ENABLE_MMX the defaults for 32bit builds
on intel hosts (the host can be AMD64, as long as the target is 32bits.)
Move mac nasm search into the mac section of the cmake code and stop
defaulting to /usr/bin/nasm, this was screwing up the build on msys2.
Fix src/filters/2xSaImmx.asm to compile and link correctly.
Add nasm to list of mingw deps for ./installdeps-msys2 .
Tested that msys2-built Wx binary runs, including with 2xSaI.
Keyboard doesn't work yet on msys2 builds, but that's a completely
different issue.
902a7a7e0d