build: Correct some targets and their rules to prevent unneeded rebuilds.

[68420948]

Without this patch the binaries are linked anew and the manpage gets recreated with every 'make' and 'make install' call, even if no changes to the sources have happened.

[streambinder]

Hey, please, fix your commit message to be Conventional Commits compliant :)

[streambinder]

Please, create separate PRs for each :) Let's keep this one for the PR about Makefile modifications

[68420948]

I've updated the PR's title. Let me know if more is needed.

[streambinder]

Unfortunately that's not enough. In order to update the commit message you can use git commit --amend and then git push -f. But please, split the PR in two different ones :)

[68420948]

Hope this is correct now.

[68420948]

Next try

[streambinder]

Thanks!