Improve `--cyclonedx` output option

Running scancode-toolkit-31.0.0b5 on MacOS 11.6.6
The --json-pp output option works fine, but
the --cyclonedx output option fails.

scancode-toolkit-31.0.0b5 % ./scancode --license --copyright --cyclonedx scancode_results_cyclonedx.json samples
Setup plugins...
Collect file inventory...
Scan files for: licenses, copyrights with 1 process(es)...
[####################] 66
ERROR: failed to run output plugin: cyclonedx:
Traceback (most recent call last):
File "//scancode-toolkit-31.0.0b5/src/scancode/cli.py", line 1067, in run_codebase_plugins
plugin.process_codebase(codebase, **kwargs)
File "//scancode-toolkit-31.0.0b5/src/formattedcode/output_cyclonedx.py", line 735, in process_codebase
bom = CycloneDxBom.from_codebase(codebase)
File "//scancode-toolkit-31.0.0b5/src/formattedcode/output_cyclonedx.py", line 633, in from_codebase
packages = codebase.attributes.packages
AttributeError: 'CodebaseAttributes' object has no attribute 'packages'

Scanning done.
Summary: licenses, copyrights with 1 process(es)
Errors count: 0
Scan Speed: 1.12 files/sec.
Initial counts: 44 resource(s): 33 file(s) and 11 directorie(s)
Final counts: 44 resource(s): 33 file(s) and 11 directorie(s)
Timings:
scan_start: 2022-06-08T180404.780531
scan_end: 2022-06-08T180436.257832
setup_scan:licenses: 2.00s
setup: 2.00s
scan: 29.42s
total: 31.49s
Removing temporary files...done.