android: add libloader to libGLES_mesa and libmesa_egl_dri2

This fixes
  src/egl/drivers/dri2/platform_android.c:664: error: undefined reference to 'loader_set_logger'
  src/egl/drivers/dri2/platform_android.c:678: error: undefined reference to 'loader_get_driver_for_fd'

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>