mesa: LLVM_DEFAULT usage

[Jan Beich]

Gunther Nikl <gnikl at justmail.de> writes:

> While testing the phabricator differential for mesa-dri/mesa-libs (D19100),
> I noticed that I don't understand it's dependency on LLVM. I assumed that
> the referenced LLVM version is required to build the ports, but the build
> used cc from base unless I added explicitly set CC and CXX as done in the
> PPC block. Only llvm-config from the referenced port is used. Is this
> intentional?
> I am using 11.3-RELEASE AMD64.

See https://wiki.freebsd.org/WhyDoIHaveToBuildLLVMWhenIAlreadyHaveClangInstalled

$ fgrep -rl libLLVM /usr/local/lib/dri                                                                    ~
/usr/local/lib/dri/vmwgfx_dri.so
/usr/local/lib/dri/r600_dri.so
/usr/local/lib/dri/radeonsi_drv_video.so
/usr/local/lib/dri/swrast_dri.so
/usr/local/lib/dri/radeonsi_dri.so
/usr/local/lib/dri/r300_dri.so
/usr/local/lib/dri/r600_drv_video.so
/usr/local/lib/dri/kms_swrast_dri.so

New Intel driver called "iris" uses libLLVM, too.