build: overlay testing/testing.go for defer in loop

compiler/internal/build/overlay.go

@@ -7,11 +7,15 @@ import (
 //go:embed _overlay/go/parser/resolver.go
 var go_parser_resolver string
 
+//go:embed _overlay/testing/testing.go
+var testing_testing string
+
 //go:embed _overlay/net/textproto/textproto.go
 var net_textproto string
 
 var overlayFiles = map[string]string{
 	"math/exp_amd64.go":          "package math;",
 	"go/parser/resolver.go":      go_parser_resolver,
+	"testing/testing.go":         testing_testing,
 	"net/textproto/textproto.go": net_textproto,
 }