Add LLVM_ARC_PATH simular MESA_ARC_PATH
Since osmesa is usually build with llvm , it will be better have similar
option for llvm as for mesa i.e in config.sh/vtk add LLVM_ARCH_PATH
similar to MESA_ARCJ_PATH
Since osmesa is usually build with llvm , it will be better have similar
option for llvm as for mesa i.e in config.sh/vtk add LLVM_ARCH_PATH
similar to MESA_ARCJ_PATH