set a standard hostname to avoid diffs

sometimes apps include the hostname in the build: https://verification.f-droid.org/org.videolan.vlc_13060406.apk.diffoscope.html#resources.arsc

This diff is because the buildserver VM has a hostname of bookworm while the verification container has a hostname based on the appid/versionCode org.videolan.vlc_13060406_pod.

We could standardize on a host name like org.videolan.vlc_13060406 to eliminate that diff. Or nag upstreams to fix. Or both

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