audio/flac: fix build of x86 intrinsic-optimized code for clang 14+

Add upstream fix "Assume Clang supports x86 intrinsics up to FMA"
to keep support for SSSE3, AVX2, etc. when compiled with clang
versions 14 and later.

Obtained from: https://github.com/xiph/flac/commit/90c0562d4eb302b01d9b82c75a7f6a66261c5546
MFH: 2022Q4

(cherry picked from commit 482804eb2cc0482d2e0e87dfc9d1e7bf6eb78d02)