javah goal does not work on jdk10+

[n-e-g]

Since jdk10 there is no javah tool anymore, and it is replaced with javac -h.
NAR plugin does not work then with newer JDKs.
There are couple of possible solutions:

• either customize plugin with command args (but this requires changing -d flag in old javah)
• create a flag in configuration to use new vs old syntax
• autodetect JDK (if javac exists but javah does not, switch to new behavior)

I could provide a patch for this, but need some guidelines which approach seems to be better

[devurandom]

This seems to be a duplicate of #313.

See #313 (comment) for a workaround