cd target/ before doing the code-signing

This is so that ./build.py clean will remove any logs or temporary directories
Disable jar-signing in update-version target
Remove Empty menu. (see #12157)
Merge pull request #2241 from manics/more_webstart_codesigning_tweaks

Run the code-signing script from the target dir
Merge pull request #2246 from jburel/view-menu

Remove Empty menu. (see #12157)