force singlethreading during precompilation

[IanButterworth]

Only allowing 1 julia thread during precompiling packages makes sense in the context that

• Pkg.precompile manages multi-processing, and any multithreading during precompilation risks overloading the system
• The upcoming LLVM image parallel PR Parallelize LLVM image generation #47797 has it's own JULIA_IMAGE_THREADS env var for controlling that multithreading, which Pkg.precompile will be taught to manage

And a niche issue:

• Allowing multiple threads (as julia currently does) causes all threads to light up in modes where no sysimage is present: incremental = false mode causes Pkg.precompile to overload all threads when multithreading PackageCompiler.jl#778

A pkgeval run would probably be a good idea for this

[IanButterworth]

It seems the -t arg doesn't propagate through julia_cmd() so I've switched it over to JULIA_NUM_THREADS

$ ./julia -t2

julia> Base.julia_cmd()
`/home/ian/Documents/GitHub/julia/usr/bin/julia -Cnative -J/home/ian/Documents/GitHub/julia/usr/lib/julia/sys.so -g1`

[DilumAluthge]

It seems the -t arg doesn't propagate through julia_cmd()

Is this a separate bug that we should fix?

[IanButterworth]

Discussed on slack and it seems logical that it doesn't. julia_cmd() only propagates declared args, not promising all are, and propagating -t to subprocesses doesn't seem to make sense.

[IanButterworth]

@nanosoldier runtests()

[nanosoldier]

Your package evaluation job has completed - possible new issues were detected.
A full report can be found here.

[IanButterworth]

pkgeval seems ok to me

[vtjnash]

                              "JULIA_NUM_THREADS" => nothing),