[fix] Install to location other than /usr/local.

[Dehim1]

I had trouble installing liboprf to a location other than /usr/local.
Uninstall also gave some errors and had weird behavior as it copied files to the installation directory.

This PR fixes these issues.

I also added src/liboprf.so.debug to the .gitignore as this file isn't tracked by the repo.

[stef]

thank you for this. one question, why do you have troubles installing somewhere else than /usr/local when using both DESTDIR and PREFIX env vars?

i note, you use pkgconf before the check if it is available.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Dehim1]

thank you for this. one question, why do you have troubles installing somewhere else than /usr/local when using both DESTDIR and PREFIX env vars?

First the issue was that sodium.h couldn't be found when running make.
Then I got "cannot find -lsodium: No such file or directory"
Then, when running make install, liboprf.pc wasn't updated, so it still had prefix=/usr/local on top.

i note, you use pkgconf before the check if it is available.

Fixed that now.