Revert "[compiler-rt] Disable tests for unavailable builtins (#158664)"

This reverts commit e9e166e54354330c474457711a8e7a7ca2efd731,
and the follow-up fix 656707086e5f6fccd2eb57f5aaf987c328c0f4f1.

These changes unlocked tests to run on architectures where they
didn't run before, showing up as test failures like in
https://lab.llvm.org/buildbot/#/builders/66/builds/19787.

GitOrigin-RevId: f7e8350f0bcbe46a046cbedfef1e6e56928ea87b