unbundle: add GN files for flac, harfbuzz-ng, and libwebp

tools/generate_shim_headers/generate_shim_headers.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 Generates shim headers that mirror the directory structure of bundled headers,
 but just forward to the system ones.
 
 This allows seamless compilation against system headers with no changes
@@ skipping 47 matching lines @@
         (header_filename,
          include_before,
          include_after) = header_spec.split(';', 2)
       else:
         header_filename = header_spec
         include_before = ''
         include_after = ''
       if options.outputs:
         yield os.path.join(target_directory, header_filename)
       if options.generate:
-        with open(os.path.join(target_directory, header_filename), 'w') as f:
+        header_path = os.path.join(target_directory, header_filename)
+        header_dir = os.path.dirname(header_path)
+        if not os.path.exists(header_dir):
+          os.makedirs(header_dir)
+        with open(header_path, 'w') as f:
           f.write(SHIM_TEMPLATE)
 
           if options.define:
             for define in options.define:
               key, value = define.split('=', 1)
               # This non-standard push_macro extension is supported
               # by compilers we support (GCC, clang).
               f.write('#pragma push_macro("%s")\n' % key)
               f.write('#undef %s\n' % key)
               f.write('#define %s %s\n' % (key, value))
@@ skipping 19 matching lines @@
               # by compilers we support (GCC, clang).
               f.write('#pragma pop_macro("%s")\n' % key)
 
 
 def DoMain(argv):
   return '\n'.join(GeneratorMain(argv))
 
 
 if __name__ == '__main__':
   DoMain(sys.argv[1:])