In a bunch of cases we create a series of sample libraries named "a",
"b", "c" etc.
This breaks on musl. Originally reported with muon via commit
ca5c371714
and also breaks the testsuite when packaging meson for alpine linux.
libc.so is an existing library which is linked in by default for all the
obvious reasons. You can get away with this on glibc, because that
includes a soversion of "6", but it loads the wrong library on musl.
D lang compilers have an option -release (or similar) which turns off
asserts, contracts, and other runtime type checking. This patch wires
that up to the b_ndebug flag.
Fixes#7082