Flang currently doesn't build in debug mode on GCC 15 due to missing
dynamic libraries in some CMakeLists.txt files, and OpenMP doesn't link
in debug mode due to the atomic library pulling in libstdc++ despite an
incomplete attempt in the CMakeLists.txt to disable glibcxx assertions.
This PR fixes these issues and allows Flang and the OpenMP runtime to
build and link on GCC 15 in debug mode.
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Co-authored-by: ronlieb <ron.lieberman@amd.com>
304373fb6d