Partial compatibility for on-device builds.
There is no guarantee that it will be possible to build all available
packages and built packages will have same reliability that cross-compiled
but should solve "self-hosting" problems as much as possible.
* Do not re=download release files.
* Efficiently handle dependencies: do not try to download \*.deb files when they already downloaded, do not try to extract them more than one time.
Addition for cada4be0d87bc4bf8559f08304d6051624d43737.
Release file may not exist too when metadata generation is in progress,
so we may need to do several tries to download file.
If previous build create metadata generation job, the repository will be left in
unsigned state for up to 5-20 seconds. We cannot do anything with this as how
Bintray works. When this case happens, signature checks will fail causing build
failure.
See https://gitlab.com/termux-mirror/termux-packages/-/jobs/175356747.
For now, gpg checks are permanently disabled. When a better solution will be
found, feel free to revert this commit.
