configure: Test if $make actually exists

configure: Test if $make actually exists

configure doesn't detect if $make is installed on the build host.
This is also helpful for hosts where an alias for make is used, i.e.
configure would fail if gmake is not present on macOS.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20200825202755.50626-5-r.bolshakov@yadro.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>