exp/ebnflint: skip test if spec is not found

Fixes golang/go#38182.

Change-Id: I79dc349fe2352408f97824b2de30e213de37160f
Reviewed-on: https://go-review.googlesource.com/c/exp/+/226677
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
diff --git a/ebnflint/ebnflint_test.go b/ebnflint/ebnflint_test.go
index 875dbc1..91fb363 100644
--- a/ebnflint/ebnflint_test.go
+++ b/ebnflint/ebnflint_test.go
@@ -5,12 +5,18 @@
 package main
 
 import (
+	"os"
 	"runtime"
 	"testing"
 )
 
 func TestSpec(t *testing.T) {
 	if err := verify(runtime.GOROOT()+"/doc/go_spec.html", "SourceFile", nil); err != nil {
+		if os.IsNotExist(err) {
+			// Couldn't find/open the file - skip test rather than
+			// complain since not all builders copy the spec.
+			t.Skip("spec file not found")
+		}
 		t.Fatal(err)
 	}
 }