Correct global excludes not always being excluded

Test: bp2build go tests
Fixes: 266617441
Change-Id: I82418ef8da4cca880d5adac98853805a18a9780e
diff --git a/bp2build/testing.go b/bp2build/testing.go
index c340a8f..92a9bf1 100644
--- a/bp2build/testing.go
+++ b/bp2build/testing.go
@@ -258,6 +258,7 @@
 }
 
 func (b BazelTestResult) CompareBazelTargets(t *testing.T, description string, expectedContents []string, actualTargets BazelTargets) {
+	t.Helper()
 	if actualCount, expectedCount := len(actualTargets), len(expectedContents); actualCount != expectedCount {
 		t.Errorf("%s: Expected %d bazel target (%s), got %d (%s)",
 			description, expectedCount, expectedContents, actualCount, actualTargets)