spinfinity: use logo file passed to configure

At the moment we hardcode the header to a logo file that ships
in fedora.

This commit changes it to use the logo configured by the distro.

#106
2 jobs for wip/use-logo-file in 3 minutes and 45 seconds (queued for 8 seconds)
latest
Status Name Job ID Coverage
  Build
passed debian-stable-x86_64 #13992228

00:03:01

passed fedora-x86_64 #13992227

00:03:45