Previously, the debugging version of the core image
(<build_dir>/var/run/<run_name>.core) was created by the run tool from
the common core object file
(<build_dir>/var/run/<run_name>/core-<kernel>.o). This object file,
however, was already stripped by the build system and thus didn't
contain debug info anymore. The build system also creates an unstripped
version in <build_dir>/debug/core-<kernel>.o, so we now use this one
for <build_dir>/var/run/<run_name>.core.
Ref #2254
91a8c8975d