ARROW-15497: [C++][Homebrew] Use Clang Tools 12
ARROW-15497: [C++][Homebrew] Use Clang Tools 12

We upgraded Clang Tools version to 12 from 8 in ARROW-14897.

Closes #12288 from kou/cpp-homebrew-llvm

Authored-by: Sutou Kouhei <73218711cdd5d5c30ac66da3cc4d9d9204caf34b@clear-code.com>
Signed-off-by: Sutou Kouhei <73218711cdd5d5c30ac66da3cc4d9d9204caf34b@clear-code.com>

wesm/arrow,icexelloss/arrow,icexelloss/arrow,icexelloss/arrow,icexelloss/arrow,kou/arrow,laurentgo/arrow,wesm/arrow,wesm/arrow,wesm/arrow,laurentgo/arrow,apache/arrow,apache/arrow,laurentgo/arrow,apache/arrow,apache/arrow,laurentgo/arrow,icexelloss/arrow,wesm/arrow,apache/arrow,laurentgo/arrow,kou/arrow,kou/arrow,laurentgo/arrow,apache/arrow,laurentgo/arrow,icexelloss/arrow,apache/arrow,apache/arrow,wesm/arrow,apache/arrow,icexelloss/arrow,icexelloss/arrow,wesm/arrow,kou/arrow,wesm/arrow,wesm/arrow,apache/arrow,wesm/arrow,kou/arrow,laurentgo/arrow,icexelloss/arrow,kou/arrow,laurentgo/arrow,icexelloss/arrow,kou/arrow,kou/arrow,wesm/arrow,icexelloss/arrow,wesm/arrow,apache/arrow,laurentgo/arrow,icexelloss/arrow,kou/arrow,apache/arrow,kou/arrow,icexelloss/arrow,kou/arrow,wesm/arrow,kou/arrow,apache/arrow,icexelloss/arrow,kou/arrow,laurentgo/arrow,apache/arrow,laurentgo/arrow,laurentgo/arrow,laurentgo/arrow,wesm/arrow,laurentgo/arrow,kou/arrow