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

pylib/gyp/generator/ninja.py

Index: pylib/gyp/generator/ninja.py
===================================================================
--- pylib/gyp/generator/ninja.py	(revision 1429)
+++ pylib/gyp/generator/ninja.py	(working copy)
@@ -738,6 +738,14 @@
         [QuoteShellArgument('-I' + self.GypPathToNinja(i), self.flavor)
          for i in include_dirs])
 
+    library_dirs = config.get('library_dirs', [])
+    if self.flavor == 'win':
+      library_dirs = self.msvs_settings.AdjustLibraryDirs(library_dirs,
+                                                          config_name)
+    self.WriteVariableList('libs',
+        [QuoteShellArgument('-L' + self.GypPathToNinja(l), self.flavor)
+         for l in library_dirs])
+
     pch_commands = precompiled_header.GetPchBuildCommands()
     if self.flavor == 'mac':
       self.WriteVariableList('cflags_pch_c',