[WIP] Add script to set the correct ulimit on Mac OS

[LorenzMeier]

This does not have automation yet.

Using call or shell or a direct call didn't work in the Makefile - likely because it is a different process group. Checking the user's bash config and appending if missing would be one way to do it (along with a bash restart).

[LorenzMeier]

This fixes the "too many open files" error on Mac OS if you call this script once in the shell per session.

[dagar]

FYI @ryanjAA

[ryanjAA]

I couldn’t get this to work with this script. I had to make several other changes (on any version of Mac OS >10.13) to increase both the number of open files and processes (processes probably not needed but done for good measure although both can have system performance concerns). Had to add two plist files to /Library/LaunchDaemons/ and then load them which also meant changing ownership of them to root:wheel After that though changing was easy and building was error free.

[dagar]

We might as well merge this until we have a more permanent/integrated solution.

[ryanjAA]

This is what I ended up following to get it working. Ive seen a few more reports on slack of people having the issue and this is how I solved it:
https://wilsonmar.github.io/maximum-limits/

[LorenzMeier]

@hamishwillee Could you please add this to the docs?

[hamishwillee]

@LorenzMeier Sure, please check PX4/PX4-Devguide#748