[ubsan] Make sigaction.cpp test UNSUPPORTED rather than XFAIL
The test fails on some builders but not on others; there's likely some
kind of environment dependence that should be investigated.
See https://reviews.llvm.org/D155317
diff --git a/compiler-rt/test/ubsan/TestCases/Misc/Linux/sigaction.cpp b/compiler-rt/test/ubsan/TestCases/Misc/Linux/sigaction.cpp
index bb420f7..db17b5d 100644
--- a/compiler-rt/test/ubsan/TestCases/Misc/Linux/sigaction.cpp
+++ b/compiler-rt/test/ubsan/TestCases/Misc/Linux/sigaction.cpp
@@ -5,7 +5,7 @@
// The test seems to segfault on aarch64 with tsan:
// https://lab.llvm.org/buildbot/#/builders/179/builds/6662
// Reason unknown, needs debugging.
-// XFAIL: target=aarch64{{.*}} && ubsan-tsan
+// UNSUPPORTED: target=aarch64{{.*}} && ubsan-tsan
#include <assert.h>
#include <signal.h>
