build: Change version strings to not have plus in them (ref #6758) (#6760)
build: Change version strings to not have plus in them (ref #6758) (#6760)

Currently a random dev version has a version string like this:

	v1.7.0-rc.1+23-gef3441bd6

That is, the tag name followed by a plus sign and the git describe
metadata (number of commits and hash) plus -dirty or -branchname in some
cases.

We introduced the plus sign in #473, where a dev version would
previously be called v0.9.0-42-gwhatever which is considered older than
v0.9.0 and hence caused a downgrade. The problem with the plus is that
per semver everything after the plus is ignored as build metadata, which
means we won't upgrade from v1.7.0-rc.1 to v1.7.0-rc.1+22-g946170f3f.

With this change the we instead either just add a dev suffix (if we're
already on a prerelease version) or we wind the patch version and add a
dev suffix.

	v1.7.0-rc.1+23-gef3441bd6 => v1.7.0-rc.1.dev.23.gef3441bd6
	v1.6.1+80-gef3441bd6      => v1.6.2-dev.80.gef3441bd6

This should preserve the ordering and keep versions semver-ish.

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