One can select a testcase by ID when running a jtreg test case directly from jtreg (using the testcase.java#testID syntax). However, this has not been possible to do when launching jtreg indirectly from make.

This fix attempts to address this issue. I have not tested this thoroughly yet, I wanted to show the code to get feedback first. The idea is to *not* emulated destructive imperative assignments through the use of eval. I instead try to handle it in a functional style without reassigning variables. I have tried to make the change as small as possible.

I am not used to change the build system, so I would appreciate thorough review.