Make generators robust in the face of generator_flags being defined....

trunk/pylib/gyp/generator/make.py

 #!/usr/bin/python
 
 # Notes:
 #
 # This is all roughly based on the Makefile system used by the Linux
 # kernel, but is a non-recursive make -- we put the entire dependency
 # graph in front of make and let it figure it out.
 #
 # The code below generates a separate .mk file for each target, but
 # all are sourced by the top-level Makefile.  This means that all
@@ skipping 712 matching lines @@
 
 
   def FixupArgPath(self, arg):
     if '/' in arg or '.h.' in arg:
       return self.Absolutify(arg)
     return arg
 
 
 def GenerateOutput(target_list, target_dicts, data, params):
   options = params['options']
-  generator_flags = params['generator_flags']
+  generator_flags = params.get('generator_flags', {})
   builddir_name = generator_flags.get('output_dir', 'out')
 
   # TODO:  search for the first non-'Default' target.  This can go
   # away when we add verification that all targets have the
   # necessary configurations.
   default_configuration = None
   for target in target_list:
     spec = target_dicts[target]
     if spec['default_configuration'] != 'Default':
       default_configuration = spec['default_configuration']
@@ skipping 20 matching lines @@
     writer.Write(qualified_target, output_file, options.depth, spec, configs)
 
     # Our root_makefile lives at the source root.  Compute the relative path
     # from there to the output_file for including.
     submakefile_path = gyp.common.RelativePath(output_file, options.depth)
     root_makefile.write('include ' + submakefile_path + "\n")
 
   root_makefile.write(SHARED_FOOTER)
 
   root_makefile.close()