par2cmdline-git :: fix check, run on 1 thread

When running with MAKEFLAGS != -j1 the tests most likely will be run out
of order which results in a failure.

Signed-off-by: BlackEagle <ike.devolder@gmail.com>
par2cmdline-git :: 20130613.4757df7-1

Signed-off-by: BlackEagle <ike.devolder@gmail.com>