Fetch NLopt when not available (and fix compiler warnings)

[Butakus]

Hi,

This PR tries to solve a major issue with the package releases: the nlopt library is not available for RHEL, so those packages are not being built (and we are reminded of it every day by the buildfarm).

When the package is not available in the system (when find_package fails), it is downloaded at build time and compiled via CMake's FetchContent. The prefered option is still getting the package via find_package, but this allows using the library when not available.

Additionally, I fixed some compiler warnings about using uninitialized variables (parameters) and a couple of unused variables.

[codecov]

Codecov Report

❌ Patch coverage is 94.59459% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...src/easynav_serest_controller/SerestController.cpp	0.00%	2 Missing ⚠️

📢 Thoughts on this report? Let us know!

[Butakus]

I see some of the warnings have been already fixed in #76 🚀

I will merge and resolve conflicts so we can add the NLopt stuff.

[fmrico]

Why the changes in the SerestController?

[Butakus]

Why the changes in the SerestController?

I got them before your fix in #76. It goes further by avoiding unnecesary local variables goal_pos_tol and goal_yaw_tol.

Same with the param changes in AMCL localizers, I just made the param declaration more homogeneous.

In both cases, the behavior remains the same.

[fmrico]

Ok. LGTM then. Let's wait for CI in green and then merge

[fmrico]

One more question, @Butakus : Why reverting the get_safe call?

[Butakus]

One more question, @Butakus : Why reverting the get_safe call?

Oooooops! That was a typo when merging, thanks for the catch!!

[Butakus]

All green now. Merging! 🚀