Fix homebrew pathing related to libomp

[phated]

When setting up noir, I was getting build failures with the native backend. This seems to be related to bad pathing on homebrew installations.

When I installed libomp with homebrew, I got this message:

libomp is keg-only, which means it was not symlinked into /Users/phated/brew, because it can override GCC headers and result in broken builds.

This means that libomp wasn't symlinked into the /Users/phated/brew/lib directory where the cmake files expected it. I've changed it to the result of brew --prefix libomp which is the actual installation location.

Additionally, the build.rs file has a hardcoded homebrew location, instead of using the brew prefix, so I fixed that.

[jfecher]

I can confirm this builds correctly on my M1 Pro as well

[jfecher]

This PR looks fine to me but I'd like more people to test building it before merging. So far it is compiling on my M1 Pro, and I cannot test on my linux machine as that is still failing from the lack of relevant header includes.

[phated]

@jfecher this should only affect Mac operating systems, everything is guarded by some sort of "apple" checks

[phated]

There's an additional argument to be made that INTEL_APPLE case should also be using brew --prefix but it'd require an intel mac + non-default homebrew setup to test it.

[vezenovm]

I am able to build locally on my intel mac from this branch. I can test changing INTEL_APPLE to use brew --prefix as well in a moment

[vezenovm]

I am able to build locally on my intel mac from this branch. I can test changing INTEL_APPLE to use brew --prefix as well in a moment

So it does build when I use find_brew_prefix for the INTEL_APPLE case. Running brew --prefix locally gives me /usr/local, so I replaced this in PR #12. I branched off of this PR, once you take a look feel free to merge it into this branch.

[phated]

Thanks for testing and adding the intel mac patch @vezenovm 🙇 This should be ready for approvals

[kobyhallx]

LGTM 👍