Add gyp target for the multidex support library.

BUG=272790

Change-Id: Id75911e76970912bb877039f09e8a2d27697cf83
Reviewed-on: https://chromium-review.googlesource.com/286032
Reviewed-by: Aurimas Liutikas <aurimas@chromium.org>
Commit-Queue: Aurimas Liutikas <aurimas@chromium.org>
Tested-by: Aurimas Liutikas <aurimas@chromium.org>
Reviewed-by: Chris Hopman <cjhopman@chromium.org>