Created attachment 140466 [details]
meson build log
mesa-git master rev 4695984dbc
buildscript used : https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=mesa-git
building with mesa-git rev 2854c0f795 worked.
src/gallium/targets/opencl/meson.build:36:0: ERROR: C++ library 'clangCodeGen' not found
Problem was with meson, builds fine with meson 0.47.1 .