Adds support for the library_dirs key, which appears in the documentation but was never actually im…

test/mac/library_dirs/subdir/test.gyp

+# Copyright (c) 2012 Google Inc. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+  'targets': [
+    {
+      'target_name': 'libraries-test',
+      'type': 'executable',
+      'sources': [
+        'hello.cc',
+      ],
+      'link_settings': {
+        'libraries': [
+          'libcrypto.dylib',
+          'libfl.a',
+        ],
+      },
+    },
+    {
+      # This creates a static library and puts it in a nonstandard location for
+      # libraries-search-path-test.
+      'target_name': 'mylib',
+      'type': 'static_library',
+      'sources': [
+        'mylib.c',
+      ],
+      'postbuilds': [
+        {
+          'postbuild_name': 'Make a secret location',
+          'action': [
+            'mkdir',
+            '-p',
+            '${SRCROOT}/../secret_location',

[Mark Mentovai, 2012/07/17 19:58:34]

Dumping stuff into the source tree is bad news. Can you come up with a way to
test this that doesn’t do that?

[Brian Ellis, 2012/07/17 20:26:52]

Hm, most of this is copied directly from test/mac/libraries/subdir/test.gyp... 
I think the reason they did it this way is that if I put the lib in ${OBJROOT}
or the like, it'll get picked up by gyp by default even without setting the
library search paths.  It's possible we could bury it in a subdirectory of
${OBJROOT} instead, but my tests indicate that will only work with Xcode because
OBJROOT isn't in the environment otherwise (frankly I'm not sure how make or
ninja deal with ${SRCROOT} either, but it appears they do somehow).  Any
suggestions?

+          ],
+        },
+        {
+          'postbuild_name': 'Copy to secret location, with secret name',
+          'action': [
+            'cp',
+            '${BUILT_PRODUCTS_DIR}/${EXECUTABLE_PATH}',
+            '${SRCROOT}/../secret_location/libmysecretlib.a',
+          ],
+        },
+      ],
+    },
+    {
+      'target_name': 'libraries-search-path-test',
+      'type': 'executable',
+      'dependencies': [ 'mylib' ],
+      'sources': [
+        'hello.cc',
+      ],
+      'library_dirs': [
+        'secret_location',
+      ],
+      'link_settings': {
+        'libraries': [
+          'libmysecretlib.a',
+        ],
+      },
+    },
+  ],
+}