[cmake] add dependency from man to revisiontag

[mwhudson]

Without this the target can run before version.py is generated, causing the build to fail. This has started happening in Debian/Ubuntu recently for some unclear reason, but what is clear is that this only ever worked by chance.

[nicolaje]

Thanks Michael @mwhudson

@dgerod I think this is important for having morse installable via apt-get, see: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=867496

but I don't understand what it does.

Also, they mention:

There is still a problem though, because the orig tarball is from the git
tag not the release tarball from
ftp://ftp.openrobots.org/pub/openrobots/morse/ there is no version.py in
the orig and the version reported in version.py is bogus:

mwhudson@scw-4e4aeb:~$ cat x/usr/lib/python3/dist-packages/morse/version.py
VERSION="UNKNOWN-dirty"
PROJECT_STABLE=False

I don't get what/where "the orig tarball from the git tag" is, but shouldn't we add a more recent release on the ftp? 1.4 is 2 years old. @pierriko @adegroote @severin-lemaignan

[severin-lemaignan]

In any case, the PR can be merged. Sorry it tooks such a long time! @nicolaje let's open another issue for the debian prbl.

[severin-lemaignan]

The version.py issue is tracked here: #782