cmd/macos-roots-test, ebnflint: fix tests so trybots work

Trybots used to work on the exp repo. Fix this to restore trybots
passing.

Change-Id: I06240de6cb1c526236c7a0e0a6c7f0d44498c1a3
Reviewed-on: https://go-review.googlesource.com/c/163302
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

cmd/macos-roots-test/main.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build darwin
+
 // Command macOS-roots-test runs crypto/x509.TestSystemRoots as a
 // stand-alone binary for crowdsourced testing.
 package main

ebnflint/ebnflint_test.go

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Doesn't work from Go 1.11 on, so...
+// +build !go1.11
+
 package main
 
 import (