Build cobol-check as GraalVM native-image

[0xE282B0]

Hi, I was testing cobol-check for the gnucobol language track of the exercism.org learning platform. I'm concerned that installing a Java program would cause support requests to set up a local environment. Therefore I'd suggest building cobol-check as GraalVM native-image.

I already tried it successfully with this branch, is this a contribution you would be interested in?