Add gyp machinery to build with packed ARM relative relocations.
Add gypi and python files to support packing ARM relative relocations
during the build process.
Define a use_relocation_packer gyp variable to turn ARM relocation
packing on and off (currently set to 0).
BUG=385553
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=281286
Review URL: https://codereview.chromium.org/
358863002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@281433 0039d316-1c4b-4281-b951-d872f2087c98