Stage 2's softfloat support still had a couple of gaps, which were
preventing us from lowering `f16` on this target. With any luck,
this is enough to get PPC64 working as a Tier 2 target again.
These defines are present on some FreeBSD systems, regardless of
whether the system is big- or little- endian. This was causing the
FreeBSD CI to be incorrectly flagged as big-endian.
Resolves https://github.com/ziglang/zig/issues/11391