[aapt2] Add --non-updatable-system flag

This adds `updatableSystem="false"` to the root <manifest> tag if no
versionCode is specified (either explicitly or through --version-code).
This attribute makes the APK not updatable (see b/266131956).

Bug: 328302305
Test: atest aapt2_tests
Test: Manually ran `aapt2 link --non-updatable-system` and verified the
resulting APK.

Change-Id: I51cdbcdac7c03de10aac9bc22f5081e12fa142ab
4 files changed