Reapply [compiler-rt] Check for and use -lunwind when linking with -nodefaultlibs (#66584)

If libc++ is available and should be used as the ubsan C++ ABI library,
the check for libc++ might fail if libc++ is a static library, as the
-nodefaultlibs flag inhibits a potential compiler default -lunwind.

Just like the -nodefaultlibs configuration tests for and manually adds a
bunch of compiler default libraries, look for -lunwind too.

This is a reland of #65912.