Improve error handling a bit, and fix upgrade for some (unsupported or
broken) targets.

Update "scripts: metadata: always resolve dependencies through provides
list" to new version.

Allow to use PROVIDES to replace existing packages.

The added debug information is stripped of during packaging, so it does not
increase the package size. It does however slightly change offsets in the
code, preventing the weird ash segfaults we've been seeing. Also, if the
issue returns, we'll have debug information matching the coredumps.

This patch got lost in the OpenWrt -> LEDE transition and fixes flash
writes on new UBNT PicoStations.

Backport another sysupgrade patch.

The staged sysupgrade allows to properly unmount the rootfs before writing
the new partitions. This will fix upgrades losing configuration when
parition sizes change on x86 and similar image types.

Fixes meshing over 802.11s.

This will ensure that gluon-site and gluon-autoupdater are rebuilt
correctly when GLUON_RELEASE or GLUON_BRANCH change.

The ar71xx-tiny target sets CONFIG_CLEAN_IPKG, which would delete opkg
control files required for user creation. Fix image generation and the user
creation script.

Fixes #1012