compilers/cpp: try to do a better job of detecting libc++ vs libstdc++

Currently, we hardcode libc++ for MacOS (and derivatives), and libstdc++
for all other cases. Clang had some hackery to make this work in many
cases. However, this doesn't always work, namely if you try to to use
Rust as the linker when libc++ is required.

This implementation does, as an optimization, provide a hardcoded list
of OSes we know always use libc++, and otherwise will attempt to detect
it. As a second optimization, the detected values are cached, so the
lookup is only done once

fixes: #11921

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