Galera's package build has a flawed detection of Debian package build.

Force debian via env variable.

Upstream fix on autodetection MariaDB/galera#10

master-galera/master.cfg

@@ -191,7 +191,7 @@ f_deb_build.addStep(steps.GitHub(
   submodules=True
 ))
 f_deb_build.addStep(steps.ShellCommand(name='build packages', command=["bash", "-xc", util.Interpolate("""set -e
-./scripts/build.sh -p""")], workdir='build'))
+./scripts/build.sh -p""")], workdir='build', env={'DEBIAN': '1'}))
 f_deb_build.addStep(dpkgDeb())
 f_deb_build.addStep(steps.ShellCommand(name='save_packages', timeout=7200, haltOnFailure=True, command=util.Interpolate('mkdir -p ' + '/packages/' + '%(prop:branch)s' + '/' + '%(prop:revision)s' + '/' + '%(prop:buildername)s'+ ' && cp -r debs/ sha256sums.txt /packages/' + '%(prop:branch)s' + '/' + '%(prop:revision)s' + '/' + '%(prop:buildername)s' + '/' +  ' && sync /packages/' + '%(prop:branch)s' + '/' + '%(prop:revision)s'), doStepIf=lambda step: savePackage(step, savedPackageBranches)))
 f_deb_build.addStep(steps.ShellCommand(name="cleanup", command="rm -r * .* 2> /dev/null || true", alwaysRun=True))