common: fix tests when running without any Android SDK installed

fdroid/fdroidserver!552
fdroid/fdroidserver#541
4 jobs for master in 27 minutes and 40 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #87426022
lint_format_safety_checks

00:04:05

passed #89166578
metadata_v0

00:03:48

passed #87426020
test

00:23:51

failed #87426021
metadata_v0

00:08:14