[tsan] Disable tests flaky on PPC with COMPILER_RT_DEBUG

Workaround for https://github.com/google/sanitizers/issues/1792

compiler-rt/test/tsan/signal_block.cpp

@@ -2,6 +2,10 @@
 
 // Test that a signal is not delivered when it is blocked.
 
+// FIXME: Very flaky on PPC with COMPILER_RT_DEBUG.
+// https://github.com/google/sanitizers/issues/1792
+// UNSUPPORTED: !compiler-rt-optimized && ppc
+
 #include "test.h"
 #include <semaphore.h>
 #include <signal.h>

compiler-rt/test/tsan/signal_reset.cpp

@@ -1,5 +1,10 @@
 // RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
 // UNSUPPORTED: darwin
+
+// FIXME: Very flaky on PPC with COMPILER_RT_DEBUG.
+// https://github.com/google/sanitizers/issues/1792
+// UNSUPPORTED: !compiler-rt-optimized && ppc
+
 #include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>

compiler-rt/test/tsan/signal_thread2.cpp

@@ -1,7 +1,8 @@
 // RUN: %clangxx_tsan %s -o %t && %run %t 2>&1 | FileCheck %s
 // UNSUPPORTED: darwin
 
-// It's very flaky on PPC with COMPILER_RT_DEBUG.
+// FIXME: Very flaky on PPC with COMPILER_RT_DEBUG.
+// https://github.com/google/sanitizers/issues/1792
 // UNSUPPORTED: !compiler-rt-optimized && ppc
 
 // Test case for https://github.com/google/sanitizers/issues/1540