[TSAN] Disable clone_setns test case on PPC64 RHEL 7.9 Targets

[kamaub]

Summary

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.

compiler-rt/test/tsan/Linux/clone_setns.cpp

 // RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
 
 // The test models how sandbox2 unshares user namespace after clone:
 // https://github.com/google/sandboxed-api/blob/c95837a6c131fbdf820db352a97d54fcbcbde6c0/sandboxed_api/sandbox2/forkserver.cc#L249
 // which works only in sigle-threaded processes.
 
 #include "../test.h"
 #include <errno.h>
 #include <sched.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#ifdef __linux__
+#  include <linux/version.h>
+#endif
 
+#if __PPC64__ && RHEL_MAJOR == 7 && RHEL_MINOR == 9
+#  define PPC64_RHEL7_9 1
+#endif
+
+#ifndef PPC64_RHEL7_9
 static int cloned(void *arg) {
   // Unshare can fail for other reasons, e.g. no permissions,
   // so check only the error we are interested in:
   // if the process is multi-threaded unshare must return EINVAL.
   if (unshare(CLONE_NEWUSER) && errno == EINVAL) {
     fprintf(stderr, "unshare failed: %d\n", errno);
     exit(1);
   }
   exit(0);
   return 0;
 }
+#endif
 
 int main() {
+#ifndef PPC64_RHEL7_9
   char stack[64 << 10] __attribute__((aligned(64)));
   int pid = clone(cloned, stack + sizeof(stack), SIGCHLD, 0);
   if (pid == -1) {
     fprintf(stderr, "failed to clone: %d\n", errno);
     exit(1);
   }
   int status = 0;
   while (wait(&status) != pid) {
   }
   if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
     fprintf(stderr, "child failed: %d\n", status);
     exit(1);
   }
+#endif
   fprintf(stderr, "DONE\n");
 }
 
 // CHECK: DONE