[gdb/testsuite] Remove debug prints in gdb_find_gdc

When running the gdb.dlang test-cases, and forcing gdb_find_gdc to be used
rather than dejagnu's copy (mimicing what happens with an older dejagnu
without find_gdc), I run into these debug prints:
...
Tool Root: /data/vries/gdb/leap-15-4/build
CC: gdc
...

Remove these.

Tested on x86_64-linux.