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

test/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': [
+    {
+      # This creates a static library and puts it in a nonstandard location for
+      # libraries-search-path-test.
+      'target_name': 'mylib',
+      'type': 'static_library',
+      'standalone_static_library': 1,
+      # This directory is NOT in the default library search locations. It also
+      # MUST be passed in on the gyp command line:
+      #
+      #  -D abs_path_to_secret_library_location=/some_absolute_path
+      #
+      # The gyptest itself (../gyptest-library-dirs.py) provides this.
+      'product_dir': '<(abs_path_to_secret_library_location)',
+      'sources': [
+        'mylib.cc',
+      ],
+    },
+    {
+      'target_name': 'libraries-search-path-test',
+      'type': 'executable',
+      'dependencies': [
+        # It is important to NOT list the mylib as a dependency here, because

[Mark Mentovai, 2013/05/29 13:23:07]

I don’t see how any build system would ensure that mylib is built before
libraries-search-path-test, then.

[Dimi Shahbaz, 2013/05/29 21:32:41]

That's the point of the weird structuring of this gyp file: the library is
intended to be built first, it must be already extant in order to test what
we're trying to test (library_dirs).

If gyp pointed the executable to the library it depends on via 'dependencies',
then it would also figure out the right link paths to use. What we're testing
here is that the 'library_dirs' directive correctly points to the library's
parent directory so that '-lmylib' works.

I'll comment this further.

+        # some build systems will track it down based on its product_dir,
+        # such that the link succeeds even without the library_dirs below.
+        #'mylib',
+      ],
+      'sources': [
+        'hello.cc',
+      ],
+      # Note that without this, the mylib library would not be found and
+      # successfully linked.
+      'library_dirs': [
+        '<(abs_path_to_secret_library_location)',
+      ],
+      'link_settings': {
+        'conditions': [
+          ['OS=="linux"', {
+            'libraries': [
+              '-lmylib',
+            ],
+          }, { # else
+            'libraries': [
+              '<(STATIC_LIB_PREFIX)mylib<(STATIC_LIB_SUFFIX)',
+            ],
+          }],
+        ],  # conditions
+      },
+    },
+  ],
+}