meson: Fix crash on x86-64/AVX caused by missing stack alignment definition
x64 and AVX require by default 16-byte alignment, this didn't cause a
crash earlier as the asm detection logic was just fixed in !24 (merged).
x64 and AVX require by default 16-byte alignment, this didn't cause a
crash earlier as the asm detection logic was just fixed in !24 (merged).