tflite: pkg_size: Ignore static libs and source files

https://crrev.com/c/5981742 will add a few `.a` files into tensorflow
package, but those files will not be installed onto DUT.

BUG=b:364243814
TEST=./script/pkg_size.py --board=rauru tensorflow

Change-Id: I56c0345695f55db0075c7ccf0e74af249f959c83
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/tflite/+/5998411
Commit-Queue: Tommy Chiang <ototot@google.com>
Auto-Submit: Shik Chen <shik@chromium.org>
Tested-by: Shik Chen <shik@chromium.org>
Reviewed-by: Tommy Chiang <ototot@google.com>