Revert of Enable GN check for webrtc/base (patchset #13 id:240001 of https://codereview.webrtc.org/2717083002/ )

Reason for revert:
Breaks Chromium because in Chromium we import WebRTC with rtc_include_tests=false (https://bugs.chromium.org/p/chromium/issues/detail?id=713179#c6).

Chromium uses webrtc/test/fuzzers and this CL adds test dependencies to neteq_rtc_fuzzer.

Original issue's description:
> Enable GN check for webrtc/base
>
> It's not possible to enable it for the rtc_base_approved
> target but since a larger refactoring is ongoing for webrtc/base
> this CL doesn't attempt to fix that.
>
> Changes made:
> * Move webrtc/system_wrappers/include/stringize_macros.h into
>   webrtc/base:rtc_base_approved_unittests (and corresponding
>   unit test to rtc_base_approved_unittests).
> * Move md5digest.* from rtc_base_approved to rtc_base_test_utils target.
> * Move webrtc/system_wrappers/include/stringize_macros.h (+test) into
>   webrtc/base.
> * Remove unused use include of webrtc/base/fileutils.h in
>   webrtc/base/pathutils.cc
>
> BUG=webrtc:6828, webrtc:3806, webrtc:7480
> NOTRY=True
>
> Review-Url: https://codereview.webrtc.org/2717083002
> Cr-Commit-Position: refs/heads/master@{#17766}
> Committed: https://chromium.googlesource.com/external/webrtc/+/ed754e71ae8866db641677073274e86fe704eeac

TBR=perkj@webrtc.org,tommi@webrtc.org,nisse@webrtc.org,kjellander@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:6828, webrtc:3806, webrtc:7480
NOTRY=True

Review-Url: https://codereview.webrtc.org/2838683002
Cr-Commit-Position: refs/heads/master@{#17849}
diff --git a/webrtc/system_wrappers/source/stringize_macros_unittest.cc b/webrtc/system_wrappers/source/stringize_macros_unittest.cc
new file mode 100644
index 0000000..8b103c5
--- /dev/null
+++ b/webrtc/system_wrappers/source/stringize_macros_unittest.cc
@@ -0,0 +1,35 @@
+/*
+ *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/system_wrappers/include/stringize_macros.h"
+
+#include "webrtc/test/gtest.h"
+
+// Macros as per documentation in header file.
+#define PREPROCESSOR_UTIL_UNITTEST_A FOO
+#define PREPROCESSOR_UTIL_UNITTEST_B(x) myobj->FunctionCall(x)
+#define PREPROCESSOR_UTIL_UNITTEST_C "foo"
+
+TEST(StringizeTest, Ansi) {
+  EXPECT_STREQ(
+      "PREPROCESSOR_UTIL_UNITTEST_A",
+      STRINGIZE_NO_EXPANSION(PREPROCESSOR_UTIL_UNITTEST_A));
+  EXPECT_STREQ(
+      "PREPROCESSOR_UTIL_UNITTEST_B(y)",
+      STRINGIZE_NO_EXPANSION(PREPROCESSOR_UTIL_UNITTEST_B(y)));
+  EXPECT_STREQ(
+      "PREPROCESSOR_UTIL_UNITTEST_C",
+      STRINGIZE_NO_EXPANSION(PREPROCESSOR_UTIL_UNITTEST_C));
+
+  EXPECT_STREQ("FOO", STRINGIZE(PREPROCESSOR_UTIL_UNITTEST_A));
+  EXPECT_STREQ("myobj->FunctionCall(y)",
+               STRINGIZE(PREPROCESSOR_UTIL_UNITTEST_B(y)));
+  EXPECT_STREQ("\"foo\"", STRINGIZE(PREPROCESSOR_UTIL_UNITTEST_C));
+}