runtime/trace: test requires 'go tool addr2line'

For the android/arm builder.

Change-Id: Iad4881689223cd6479870da9541524a8cc458cce
Reviewed-on: https://go-review.googlesource.com/12859Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>

src/runtime/trace/trace_stack_test.go

@@ -21,7 +21,7 @@ import (
 // In particular that we strip bottom uninteresting frames like goexit,
 // top uninteresting frames (runtime guts).
 func TestTraceSymbolize(t *testing.T) {
-	testenv.MustHaveExec(t)
+	testenv.MustHaveGoBuild(t)
 
 	buf := new(bytes.Buffer)
 	if err := Start(buf); err != nil {