Hello, This issue happened with mesa-opencl-icd 20.1.8-1, but with 20.2.0-rc4-2 with cherrypicking install(^_^;, this issue doesn't happen. This seems to be differ of linked libllvm, recent of v20.1.x links llvm10 and libclc, but recent libclc links llvm11 :-(
But, with 20.2.x, links llvm11 and libclc. So, with mesa20.1.x conflicts version of llvm/clang, with mesa20.2.x does not conflict. Please check more for my inference. Regards, Ohta.