Stop testing on COMPILER_MSVC.  The correct choice is _WIN32.

See: https://github.com/bazelbuild/bazel/issues/5351

RELNOTES: None
PiperOrigin-RevId: 316630843
diff --git a/src/test/shell/integration/output_filter_test.sh b/src/test/shell/integration/output_filter_test.sh
index 249611f..fc0ebb8 100755
--- a/src/test/shell/integration/output_filter_test.sh
+++ b/src/test/shell/integration/output_filter_test.sh
@@ -82,7 +82,7 @@
 
 int main(void)
 {
-#ifdef COMPILER_MSVC
+#ifdef _WIN32
   // MSVC does not support the #warning directive.
   int unused_variable__triggers_a_warning;  // triggers C4101
 #else  // not COMPILER_MSVC