Fix compilation in OSX Catalina with OMP enabled

[SergioRAgostinho]

• Explicitly add linker flags from OMP

[shrijitsingh99]

This problem managed to escape the macOS CI since OMP was not installed. We should add it the CI will help catch any future errors that may arise.

[SergioRAgostinho]

Go for it 👍 However, it's not worth to commit the change until we fix the problem.

[shrijitsingh99]

Go for it 👍 However, it's not worth to commit the change until we fix the problem.

Yeah true, we could just add it to this PR since its only one line (brew install libomp) added to build-macos.yml.

[SergioRAgostinho]

I'm not gonna touch this for the time being, so feel free to take over the issue and signal the closing of this PR if you get yours ready.

[taketwo]

So unlike all other OSes, Catalina needs OMP to be explicitly linked? This needs to be propagated to downstream packages then :(

[kunaltyagi]

Let's add libomp to the brew install step in the CI to make sure we're fixing the error for PCL compilation

[SergioRAgostinho]

I haven't addressed the downstream part yet i.e.: it the project is compiled with OMP and requires linking flags, the assumption is that if the linking flags are not propagated to a downstream project it will have linking issues.

Edit: I saw the new issue now. You can merge this and I can try to address it later. At least the user will be able to build PCL. He can later report if he later had linking issues.

[kunaltyagi]

I created an issue to track the potential issue. We can go ahead and merge this