Latest round of SCons generator changes: * Make sure rules, too, are built before the actual targets. * Generate a 'gyp_target_*' Alias for each target that corresponds to the   XCode-like gyp targets. * Express explicit order-only prerequisites between dependent   gyp_target_* Aliases to conform to gyp build order requirements. * Stop trying to be smart about only creating the 'prerequisites'   variable in the *.scons files when it's "necessary."  It's much   simpler to just create an empty list, extend it as necessary,   and let SCons sort out the behavior. * Refactor the _SCons_*_writer() functions a bit to commonize more code. Review URL: http://codereview.chromium.org/42042
Latest round of SCons generator changes:
* Make sure rules, too, are built before the actual targets.
* Generate a 'gyp_target_*' Alias for each target that corresponds to the
  XCode-like gyp targets.
* Express explicit order-only prerequisites between dependent
  gyp_target_* Aliases to conform to gyp build order requirements.
* Stop trying to be smart about only creating the 'prerequisites'
  variable in the *.scons files when it's "necessary."  It's much
  simpler to just create an empty list, extend it as necessary,
  and let SCons sort out the behavior.
* Refactor the _SCons_*_writer() functions a bit to commonize more code.
Review URL: http://codereview.chromium.org/42042

csulmone/gyp,csulmone/gyp,csulmone/gyp,csulmone/gyp