ac-os: don't use musl-gcc when shared libs are glibc-linked
On Ubuntu, libasound/libdrm/etc. link against glibc. Using musl-gcc
to build ac-native creates a musl binary that can't load glibc shared
libs at runtime, causing kernel panic (blinking caps lock). Now checks
if libasound links against libc.so.6 (glibc) and falls back to gcc.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>