Clockwork 1.5.3

The app is unchanged; this release makes the build reproducible. F-Droid can now verify that its own build matches the APK published here and ship that one, so the download from GitHub and the version from F-Droid carry the same signature and can update each other. Two sources of byte-level noise had to go: the ART baseline profile, which AGP does not generate deterministically, and AAPT2's PNG recompression, which differs between toolchains. The APK grows by 53 kB as a result.