LU-16969 build: check that pkg-config is installed

LU-16969 build: check that pkg-config is installed

PKG_CHECK_MODULES macro fails in very annoying to debug ways.
Often, this will fail with:

 syntax error near unexpected token `LIBNL3,'
 `	PKG_CHECK_MODULES(LIBNL3, libnl-genl-3.0 >= 3.1)'

and provide no indication that the real error is that
pkg-config is not installed. Adding an explicit check
for pkg-config will make the error more self-evident.

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Change-Id: Ic2ee8e4c3ec3fa2e03c5ece03e6a9ce335133578
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51716
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>