Change the LLVM tools version to 12 (v9.11)
LLVM 12 stable was released on 15. April 2021, change the default version to the current stable.
(cherry picked from commit 9f785532)
Edited by Ondřej Surý
LLVM 12 stable was released on 15. April 2021, change the default version to the current stable.
(cherry picked from commit 9f785532)