Fix install

[BDoignies]

PR Description

Fixing some install commands for polyscope dependancies. It also adds a step to test that system wide installation works and can be linked properly using find_package.

@dcoeurjo The test is located inside tests/projects as I couldn't think of a better name. If you have one, please let me know.

Checklist

• Unit-test of your feature with Catch.
• [N/A] Doxygen documentation of the code completed (classes, methods, types, members...)
• [N/A] Documentation module page added or updated.
• New entry in the ChangeLog.md added.
• No warning raised in Debug mode.
• All continuous integration tests pass (Github Actions)

[dcoeurjo]

thanks a lot ! tests/project is fine to me.

[BDoignies]

@dcoeurjo Should be good now. I do not exactly know what to do with codacy reports.

Should we add some useless code to remove the warnings? Any ideas on other things we should try to compile (especially for optional dependencies)?

[dcoeurjo]

Thanks @BDoignies I will have a look.
Regarding Codacy, I am inclined to remove this check... it is rarely informative for a so big C++ project...

[dcoeurjo]

Thanks for the PR, just a few questions.

[dcoeurjo]

All good. Thx again