install.sh consulted ldd before the ELF interpreter while pm/store.py's
_is_musl_libc reads the native userland's ELF interpreter first, so a
glibc ldd (secondary toolchain, gcompat) could make the bootstrap stage
a different libc than PM later resolves. Read /bin/sh (then /bin/ls)
PT_INTERP first in both; ldd and the loader glob are fallbacks only.