anv/android: fix missing dependencies issue during parallel build

The libmesa_anv_gen* modules require anv_extensions.h, patch makes sure it gets generated as a dependency before building them.

Signed-off-by: Chenglei Ren chenglei.ren@intel.com Reviewed-by: Tapani Pälli tapani.palli@intel.com Cc: mesa-stable@lists.freedesktop.org