jenkins-build-all: force-limit `fdroid build` to 6 hours

The jenkins admins have requested that the jobs have much shorter run
times.  Otherwise they will just force restart jenkins or reboot the box
when updates come, without waiting for the jobs to finish.

jenkins-build-all

@@ -95,6 +95,9 @@ else
     sed -i '/^wiki_/d' config.yml
 fi
 
+# force global timeout to 6 hours
+sed -Ei 's,^(\s+endtime\s*=\s*time\.time\(\))\s*.*,\1 + 6 * 60 * 60  # 6 hours,' fdroidserver/build.py
+
 $WORKSPACE/fdroid build --verbose --latest --no-tarball --all $wikiflag
 
 vagrant global-status