Don't compress the JIT mini-debug-info if we have just 1 method.

The compression is great help for multiple methods but
it is not worth it for single method due to overheads,
so skip the compression there for a small speed boost.

Test: testrunner.py --host -t 137
Change-Id: Idc37645061c745032474b5115e66b1d790550d0a