Remove third_party/golang.org/x/mobile as it is no longer used with Go 1.5.

third_party/go/src/golang.org/x/mobile/app/android_arm.c

-// Copyright 2014 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.
-
-// +build android,arm
-
-#include <android/log.h>
-#include <stdint.h>
-#include <string.h>
-#include "_cgo_export.h"
-
-#define AT_PLATFORM  15
-#define AT_HWCAP     16
-#define HWCAP_VFP    (1 << 6)
-#define HWCAP_VFPv3  (1 << 13)
-
-void build_auxv(uint32_t *auxv, size_t len) {
-        // Minimum auxv required by runtime/os_linux_arm.go.
-        int i;
-        if (len < 5) {
-                __android_log_print(ANDROID_LOG_FATAL, "Go", "auxv len %d too small", len);
-        }
-        auxv[0] = AT_PLATFORM;
-        *(char**)&auxv[1] = strdup("v7l");
-
-        auxv[2] = AT_HWCAP;
-        auxv[3] = HWCAP_VFP | HWCAP_VFPv3;
-        for (i = 4; i < len; i++) {
-                auxv[i] = 0;
-        }
-}