[llvm] [ci] limit parallel windows compile jobs to 24 (PR #93329)

[Tom Stellard via llvm-commits]

https://github.com/tstellar commented:

There is also `LLVM_RAM_PER_COMPILE_JOB` which might scale better if the machine sizes change, but I'm not sure if this works for Windows.

You may also want to  use LLVM_RAM_PER_LINK_JOB/LLVM_PARALLEL_LINK_JOBS too.  

https://github.com/llvm/llvm-project/pull/93329