Gradle produces signed, unaligned APK files. We expect unsigned,
unaligned APK files. This change discards any existing signature,
turning a signed, unaligned APK into an unsigned, unaligned APK.
Sadly |zip -q| does not silence a warning message about "nothing to
do" so we pipe to /dev/null.
MozReview-Commit-ID: DnSGJCvHsym
--HG--
extra : rebase_source : ee7884847767c0a075e3cfd404ba695d07f47e93
extra : histedit_source : 6aaa07eac03d69668f8556b84d1c1bae51c8ea22