Fix errors caught by go vet in compliance package

`go test` implicitly runs `go vet` and fails the tests if vet
errors are found.  Fix all the issues found by vet.

Test: go test build/make/tools/compliance/...
Change-Id: If0684cf124ece4931af440008cd44a61c22de475
diff --git a/tools/compliance/cmd/bom_test.go b/tools/compliance/cmd/bom_test.go
index 9c12671..fc61bbf 100644
--- a/tools/compliance/cmd/bom_test.go
+++ b/tools/compliance/cmd/bom_test.go
@@ -275,7 +275,7 @@
 
 			err := billOfMaterials(&ctx, rootFiles...)
 			if err != nil {
-				t.Fatalf("bom: error = %w, stderr = %v", err, stderr)
+				t.Fatalf("bom: error = %v, stderr = %v", err, stderr)
 				return
 			}
 			if stderr.Len() > 0 {