Summary and Info:
It appears as though if your license array in your PKGBUILD contains spaces, like:
license=("custom:University of Illinois/NCSA Open Source License")

and you are building split packages, makepkg will mess up on the latter's license.
After running makepkg, looking at the .PKGINFO file for each package built will show that while the first has:
license = custom:University of Illinois/NCSA Open Source License

The second has:
license = custom:University
license = of
license = Illinois/NCSA
license = Open
license = Source
license = License


This leads to the oddity that when you've installed both packages, the first package's pacman -Qi | grep Licenses:
Licenses : custom:University of Illinois/NCSA Open Source License

And the second package's pacman -Qi | grep Licenses:
Licenses : custom:University of Illinois/NCSA Open Source License


This might also cause trouble with submitting to AUR and such, I haven't tried.



Attached is a PKGBUILD which demonstrates the problem. Look in pkg/{llvm,clang}/.PKGINFO, and try `pacman -Qi {llvm,clang} | grep Licenses` after you've installed both.