meson: Set nasm version when targeting Windows
v2.12 is when nasm added support for cv8 debug support in the COFF backend. Before that, it would try to use dwarf since we pass -g and fail since that's not allowed for COFF.
https://nasm.us/doc/nasmdocc.html#section-C.1.17
Fixes #12 (closed)
Can't backport this to 4.3.1 because it requires meson >=0.52