LU-17522 build: Distribute clang build infrastructure

LU-17522 build: Distribute clang build infrastructure

Macro files:
    lustre-toolchain.m4 lustre-compiler-plugins.m4
and directory:
   cc-plugins

Should be included in distributed files, unconditionally.

Test-Parameters: trivial
Fixes: d684885098 ("LU-16961 clang: plugins and build system integration")
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I6ddedd82c6180ffd1c4134fda6af6df6bd23dd34
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/53991
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>