Workaround for non-English javadoc generation

Workaround for non-English javadoc generation

On my workstation, more recent JDKs generate partly German javadocs.

Background: Avoid non-English javadoc generation. Due to
https://bugs.openjdk.org/browse/JDK-8222793 reoccurring at least in JDKs
19-21 and also being broken in some older JDKs, we cannot rely on just
setting the locale parameter, but also need the 'user.language' and
'user.country' parameters in 'additionalJOptions' as a workaround.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>