scripts: allow java8 runtime

Acked-by: Paul Millar
Target: master, 2.9, 2.8, 2.7, 2.6
Require-book: no
Require-notes: no
(cherry picked from commit 4a838d240102db12eaa1d0fc035155e1b22495eb)
Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Merge pull request #605 from kofemann/j7-2.6

scripts: allow java8 runtime