Drop "v" from the version tag, add tilde back
    
    When -Dversion-tag was initially added in edaa157918874478659896090b9512af0c50f82e,
    I used "v" without any comment. But upstream does not use "v", so we have
    versions which don't compare directly:
    
    $ build/systemctl --version|head -n1
    systemd 251 (251-66-g7e46a5c+)
    $ systemctl --version|head -n1
    systemd 251 (v251-1.fc37)
    
    And in 3c4f9413a760fa2dc26c140a08e1d11cf46ac6e7, when -Dshared-lib-tag= was
    introduced, %{version} was replaced by %{version_no_tilde}, again without any
    specific comment. For the shared-lib-tag, it makes sense to use _no_tilde,
    because it's enough to have non-conflicting file names, and we don't compare
    the tags. I guess I wanted both uses to be consistent. But if we substitute
    the tilde, we can't do proper comparisons.
    
    I noticed the following issue: with sd-boot installed from git and a
    package, upgrades wouldn't work:
    
    Comparing versions: "systemd-boot v251-1.fc37" < "systemd-boot 251-rc1-390-g3603f15
    Skipping "/boot/efi/EFI/systemd/systemd-bootx64.efi", since newer boot loader version in place already.
    
    The two changes should make those comparisons work properly in most
    cases.