Selftest for solar_debug

[abrunnin-xilinx]

Similar to testing solar_capture and solar_capture_monitor front ends, we should have at least one test that invokes solar_debug.
This test should also check that the debug version of the library is actually being used, not just that the SC_ATTR="log_level=..." option has been set.

The start-up messages should include: "sc_session_alloc: DEBUG build"

Note: Currently, if you run directly from build-products, they do not. You'd have to actually install solar_capture. To ease testing, it might be better to improve solar_debug to also search relative to the directory it is in, when looking for the debug library.