When installing a package, even from the package manager, the default compilation flags are to use 2-CPU cores only. This might be fine for your setup, but I recently ran into an issue where qt5-webengine was taking an entire day to build on my laptop.
Make the change by setting your MAKEFLAGS to match your processor count, or at least close.
Copy makepkg.conf into your home directory as .makepkg.conf and edit accordingly (MAKEFLAGS="--jobs=$(nproc)" to use all the cores) I have 16 cores available to me, but want to have some available beyond building stuff. So I set MAKEFLAGS="--jobs=12" or -j12 in shorthand.
cp /etc/makepkg.conf ~/.makepkg.conf
As pamac/pacman run as root you may want to edit the /etc/makepkg.conf directly.
References
https://wiki.archlinux.org/title/Makepkg#Improving_build_times