LU-11880 build: allow Debian build on Raspbian

LU-11880 build: allow Debian build on Raspbian

Allow the Debian build to work on Raspbian and other Debian and
Ubuntu variants that use the same build machinery.  Add armhf
to the list of allowed CPU architectures.

Test-Parameters: trivial clientdistro=ubuntu1804
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Iedc90ad32754f81a3d387a66409f07aaa305a5b1
Reviewed-on: https://review.whamcloud.com/34085
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Thomas Stibor <t.stibor@gsi.de>
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>