dependencies: Fix detection of Python arch on MSYS
dependencies: Fix detection of Python arch on MSYS

sysconfig.get_platform() returns 'mingw' with MSYS2, so we need to
use some other method; in this case I chose to use the CC that
Python was compiled with, which is a relatively reliably indicator
unless people start using Python on Windows compiled with Clang or
something.

jpakkane/meson,QuLogic/meson,pexip/meson,jeandet/meson,MathieuDuponchelle/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,becm/meson,pexip/meson,trhd/meson,QuLogic/meson,jpakkane/meson,becm/meson,thiblahute/meson,becm/meson,ernestask/meson,ernestask/meson,jpakkane/meson,thiblahute/meson,mesonbuild/meson,jpakkane/meson,MathieuDuponchelle/meson,QuLogic/meson,mesonbuild/meson,trhd/meson,ernestask/meson,pexip/meson,jeandet/meson,mesonbuild/meson,ernestask/meson,trhd/meson,MathieuDuponchelle/meson,thiblahute/meson,thiblahute/meson,jpakkane/meson,ernestask/meson,becm/meson,pexip/meson,trhd/meson,MathieuDuponchelle/meson,QuLogic/meson,pexip/meson,becm/meson,MathieuDuponchelle/meson,thiblahute/meson,thiblahute/meson,thiblahute/meson,jeandet/meson,MathieuDuponchelle/meson,MathieuDuponchelle/meson,jpakkane/meson,becm/meson,trhd/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,thiblahute/meson,ernestask/meson,pexip/meson,QuLogic/meson,mesonbuild/meson,becm/meson,jeandet/meson,MathieuDuponchelle/meson,jeandet/meson,becm/meson,QuLogic/meson,trhd/meson,ernestask/meson,mesonbuild/meson,jeandet/meson,becm/meson,ernestask/meson,MathieuDuponchelle/meson,becm/meson,pexip/meson,jeandet/meson,jeandet/meson,mesonbuild/meson,thiblahute/meson,QuLogic/meson,trhd/meson,trhd/meson,QuLogic/meson,trhd/meson,ernestask/meson,pexip/meson,jpakkane/meson,QuLogic/meson,mesonbuild/meson,jeandet/meson,mesonbuild/meson