make: Make XcodeSettings per-target instead of per-configuration, part 1.
make: Make XcodeSettings per-target instead of per-configuration, part 1.

This makes it possible to move all the bundle path logic into XcodeSettings,
which is required if xcode_config_file ever needs to be supported. It will
also make it easier to eventually write a ninja generator, and it's
required if GetLdFlags() needs to read the results of GetXcodeEnv() (which
will be moved into XcodeSettings, too).

BUG=http://crbug.com/90043, http://crbug.com/90199
Review URL: http://codereview.chromium.org/7493049
old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google