copyright: don't require checkout to be named tools

The directory isn't named 'tools' on LUCI.

Change-Id: Ia91a77b924704496491bdf4e8306c9ac139f9f57
Reviewed-on: https://go-review.googlesource.com/c/tools/+/489755
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Heschi Kreinick <heschi@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Heschi Kreinick <heschi@google.com>

copyright/copyright_test.go

@@ -8,22 +8,12 @@
 package copyright
 
 import (
-	"os"
-	"path/filepath"
 	"strings"
 	"testing"
 )
 
 func TestToolsCopyright(t *testing.T) {
-	cwd, err := os.Getwd()
-	if err != nil {
-		t.Fatal(err)
-	}
-	tools := filepath.Dir(cwd)
-	if !strings.HasSuffix(filepath.Base(tools), "tools") {
-		t.Fatalf("current working directory is %s, expected tools", tools)
-	}
-	files, err := checkCopyright(tools)
+	files, err := checkCopyright("..")
 	if err != nil {
 		t.Fatal(err)
 	}