[libcxx] Make the GDB pretty printer test less strict

This is a workaround for PR48937. GDB can sometimes print additional
warnings which currently fails the test. Use re.search instead of
re.match to ignore this additional output.

Differential Revision: https://reviews.llvm.org/D99532

GitOrigin-RevId: 9ac988f6a80aa1dd25594a8b4c86c0380ac99466
1 file changed