The compler-rt test case tsan/Linux/clone_setns.cpp fails on
PowerPC64 RHEL 7.9 targets.
Unshare fails with errno code EINVAL.
It is unclear why this happens specifically on RHEL 7.9 and no other
operating system like Ubuntu 18 or RHEL 8.4 for example.
This patch uses marcos to disable the test case for ppc64 rhel7.9
because there are no XFAIL directives to target rhel 7.9 specifically.
Reviewed By: dvyukov
Differential Revision: https://reviews.llvm.org/D130086
Start the background thread only after fork, but not after clone.
For fork we did this always and it's known to work (or user code has adopted).
But if we do this for the new clone interceptor some code (sandbox2) fails.
So model we used to do for years and don't start the background thread after clone.
Reviewed By: melver
Differential Revision: https://reviews.llvm.org/D113744