v4.0.6

Eagle for Linux v4.0.6

A packaging release. Every package now provides the media tools Eagle's
plugins shell out to, rather than each one differing.

exiv2 is now a declared dependency
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The Exif Metadata plugin ships Windows and macOS builds of exiv2 only, and
picks the macOS one on Linux, where it cannot execute and reports "Error: 126".
ffmpeg was already declared for the equivalent reason, so exiv2 joins it: on
PATH for Nix, in Requires for rpm, in depends for Arch, and built inside the
sandbox for Flatpak.

This does not fix that plugin on its own. Its bundled binary still has to be
replaced with a wrapper; the dependency is what makes such a wrapper able to
resolve.

The AppImage now carries its tools
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An AppImage has no dependency mechanism, so it was the one package that could
silently do nothing on a host without ffmpeg or exiv2. It now ships both, plus
ffprobe, with their libraries. This adds roughly 100MB.

The core runtime is deliberately left to the host: bundling glibc alongside
the host loader is how an AppImage ends up running only on the machine that
built it. The build verifies that every other dependency resolves from inside
the bundle and that all three tools actually start, so an incomplete bundle
fails the build rather than reaching a user.

Nothing here changes application behaviour. Everything from v4.0.5 - the fix
for videos and other plugin-backed formats getting stuck on "importing" - is
included.

Fedora users need RPM Fusion for ffmpeg with proprietary codecs.