Set CMAKE_BUILD_PARALLEL_LEVEL environment variable.

[dhull]

cmake builds previously did not respect HOMEBREW_MAKE_JOBS. This change fixes that.

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---

[Bo98]

Change looks OK.

Though not entirely sure what scenario this would have applied given cmake already respects MAKEFLAGS which we set? Do you have a reproducer?

[cho-m]

Need to update deparallelize too.

As far as I can tell:

• Unix Makefiles should use MAKEFLAGS already so shouldn't be impacted
• Ninja defaults to all CPUs. We have a ninja shim but cmake --build does not use it. So setting CMAKE_BUILD_PARALLEL_LEVEL will help, but mainly for reducing the parallelization (i.e. setting a lower HOMEBREW_MAKE_JOBS or getting it working with ENV.deparallelize)
• Should allow controlling parallelization for other generators like Xcode. We don't use them in Homebrew/core but maybe 3rd party taps do.

[MikeMcQuaid]

Need to update ENV.deparallelize too (as mentioned by @cho-m).

Marking as request changes just to ensure it's not merged by mistake before that.

[dhull]

Though not entirely sure what scenario this would have applied given cmake already respects MAKEFLAGS which we set? Do you have a reproducer?

Yes.

I have a old Mac running MacOS Big Sur 11.7.10 (the latest version of the OS supported on this Mac) so homebrew needs to compile packages when I install them. My Mac has 8 cores and 16 GB RAM and some of the builds occasionally fails because they run out of memory, with 8 cmake jobs running. I tried setting CMAKE_BUILD_PARALLEL_LEVEL in my environment but discovered that brew cleared it and so it had no effect. I then tried setting HOMEBREW_MAKE_JOBS and found 8 cmake jobs still ran. Finally I made this change and then the number of cmake jobs was limited by HOMEBREW_MAKE_JOBS.

[carlocab]

We have a ninja shim but cmake --build does not use it.

Kinda weird that it doesn't, since cmake --build will happily take any ninja in PATH outside of brew.

[cho-m]

Kinda weird that it doesn't, since cmake --build will happily take any ninja in PATH outside of brew.

CMake uses find_program so some other locations take precedence over PATH like:

brew/Library/Homebrew/extend/ENV/super.rb

Lines 257 to 260 in 215064e

	def determine_cmake_prefix_path
	PATH.new(
	keg_only_deps.map(&:opt_prefix),
	HOMEBREW_PREFIX.to_s,