runtime: delete export_arm_test.go

The only thing export_arm_test.go does is to export usplit,
which does not exist in gccgo.

Change-Id: If459299d8b4402ca28bb0e1934f56ffe6723e0bd
Reviewed-on: https://go-review.googlesource.com/c/155760
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/libgo/go/runtime/export_arm_test.go b/libgo/go/runtime/export_arm_test.go
deleted file mode 100644
index b8a89fc..0000000
--- a/libgo/go/runtime/export_arm_test.go
+++ /dev/null
@@ -1,9 +0,0 @@
-// Copyright 2015 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Export guts for testing.
-
-package runtime
-
-var Usplit = usplit