[NFC] Add explicit return from main() in tests

llvm-svn: 358302
GitOrigin-RevId: 11bbb5831ba5d5823bccea7f84eaaab54276e32c
diff --git a/test/pstl/version.pass.cpp b/test/pstl/version.pass.cpp
index 15f6aeb..e57569b 100644
--- a/test/pstl/version.pass.cpp
+++ b/test/pstl/version.pass.cpp
@@ -14,4 +14,6 @@
 static_assert(_PSTL_VERSION_MINOR == 00);
 static_assert(_PSTL_VERSION_PATCH == 0);
 
-int main() { }
+int main() {
+    return 0;
+}