[libc++abi] Use __has_feature check to enable usage of thread_local for exception storage (#97591)

Previously, we'd use HAS_THREAD_LOCAL which was never defined. Hence,
we'd basically never use the code path where we use thread_local.

Fixes #78207

NOKEYCHECK=True
GitOrigin-RevId: acaa4c8bfd12eac4fa5f2c03e9d394f7bd8f1bd6
1 file changed