This should significantly speedup building the pinecone and yggdrasil
demos, as they now reuse the new `dendrite:buildcache`, which already
builds all binaries.
If I didn't mess up the workflow, this should remove some ugliness from
the version string (e.g. 0.13.2+57ddbe0.57ddbe0, dupe commit hash, as a
result of https://github.com/matrix-org/dendrite/pull/3147)
This builds on @S7evinK's work to make multi-stage Docker builds. Now
that we can build SQLite without Cgo this should be much simpler and
should make Docker builds in CI significantly faster.
Co-authored-by: Till Faelligen <tfaelligen@gmail.com>
Co-authored-by: Till Faelligen <davidf@element.io>
Co-authored-by: Till Faelligen <2353100+S7evinK@users.noreply.github.com>
