pkg/archlinux: Explicitly set /usr/lib as the library directory.
pkg/archlinux: Explicitly set /usr/lib as the library directory.

By default CMake uses /usr/lib64, which is non-standard on Arch and
results in nothing being able to find the library.

Signed-off-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Signed-off-by: Chad Versace <a557f7f75bf28dc19ac99107f5cc7cd6b3fbdb1a@linux.intel.com>

chadversary/waffle,waffle-gl/waffle,evelikov/waffle,dcbaker/waffle,yinquan529/waffle-gl-waffle,maurossi/waffle,waffle-gl/waffle,fjhenigman/waffle,waffle-gl/waffle,maurossi/waffle,janesma/waffle,janesma/waffle,fjhenigman/waffle,evelikov/waffle,chadversary/waffle,waffle-gl/waffle,janesma/waffle,evelikov/waffle,dcbaker/waffle,dcbaker/waffle,chadversary/waffle,maurossi/waffle,yinquan529/waffle-gl-waffle,yinquan529/waffle-gl-waffle,fjhenigman/waffle