LU-18813 contrib: add an example config.site

LU-18813 contrib: add an example config.site

The variable CONFIG_SITE can be used to specify
config files to the Autoconf generated configure
script. This is a useful alternative to long
configure command lines.

Add an example config.site file used for compiling
Lustre server (osd-wbcfs) and client for use in
ktest.

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: I6597b860629643ced7191d7a250a86ede2576993
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/59265
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Lijing Chen <lijinc@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>