build: overwrite clang-format version on Ubuntu 24.04

build: overwrite clang-format version on Ubuntu 24.04

clang-format-11 is used by default in checkstyle.sh while it can be
overridden to higher clang-format version. On Ubuntu 24.04, the minimum
version of clang-format is version 14. Set the environment variable
explicitly in Makefile to overwrite the clang-format version.

Before:
$ make checkstyle
extras/scripts/checkstyle.sh: line 41: --version: command not found
make: *** [Makefile:775: checkstyle] Error 127

After:
$ make checkstyle
Ubuntu clang-format version 14.0.6
*******************************************************************
* CHECKSTYLE SUCCESSFULLY COMPLETED
*******************************************************************

Type: fix

Change-Id: Iba3e4739c9376701577b2f37e070d199b195e7d0
Signed-off-by: Jay Wang <[email protected]>