Accept pkgconf difference for spaces.

* src/gpg-error-config-test.sh (OUTPUT_OLD): Use shell
and echo to remove spaces.

There is an alternative implementation of pkg-conf, named pkgconf.
It emits an extra space at the end.

Tested on FreeBSD 11.1.

• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>