android: Fix build more after 255971.

Two more ant scripts were implicitly depending on the generated
manifest file via an implicit dependency through a stamp file.
Follow-up to https://codereview.chromium.org/193163004

BUG=256020
R=cjhopman@chromium.org
TBR=cjhopman@chromium.org

Review URL: https://codereview.chromium.org/191383008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256038 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256038