Fix Java 21 FTBFS

This MR fixes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1052589

Changes:

• d/rules: use java_compat_level variable provided by java-common to adjust -source/-target level to the minimum required by the default Java (Closes: #1052589)

Testing:

• build in sid chroot with default Java 21
• build in sid chroot

added 1 commit

• 8133b628 - Update bug number in changelog to 1052617

Compare with previous version

Thank you @vpa1977 . Note that I updated the changelog entry to close bug #1052617 (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1052617)

merged

mentioned in commit 7e584d5c