PKGBUILD Question: How To Force Parallel Jobs to LLVM / Clang?

I have been compiling some packages and saw that Clang++ uses all of the cores of my CPU rising the temperature, fans etc.

How can I force LLVM to use a maximum number of cores?

I found in LLVM documentation the option:

LLVM_PARALLEL_LINK_JOBS=M

Where should it be specified?

Makepkg.conf or PKGBUILD?

I personally do not mind if it will take longer to compile. I can send the computer (laptop) doing it overnight.

Thanks