Running out of memory post-scan when scanning a large projects (~160.000 files)

### Description

While scanning a rather large project of about 160.000 files (https://github.com/Azure/azure-sdk-for-java) we are experiencing a massive usage of memory after the scan finished and before writing the result.json, leading to out of memory issues on our system.

### How To Reproduce

1.) Download the beforementioned sourcecode archive from github
2.) Run extractcode to extract the archive (and all contained archives/jars/etc.)
3.) Start the scan with scancode.
4.) Wait some hours for it to complete.
5.) Error.

Before we scanned the project we did an recursive extract of the sourcecode archive downloaded from the above mentioned URL using the following command:
`extractcode --verbose path/to/file.zip`

We are running the scan with the following command:
`scancode -clpi --license-score 65 --max-in-memory -1 -n 4 --strip-root --verbose --json-pp result.json /code`

### System configuration

* What OS are you running on? Linux (containerized on Openshift)
* What version of scancode-toolkit was used to generate the scan file? v21.3.31
* What installation method was used to install/run scancode? source download + containerization

We are running in a containerized environment, leading to hard shutdowns of the process when assigned memory resources are exceeded. Currently the application is provided a maximum of 2.2GB of memory which has been more than enough for all smaller projects we scanned thus far up to about 20.000 files.

Is there a way to optimize the writing of the json-result file so that memory issues on large projects can be avoided? Otherwise is there a workaround available in order to be able to complete these large scans?

The full error log from Scancode:
```
removing temporary files...done.
traceback (most recent call last):
file "/usr/local/lib/python3.6/multiprocessing/pool.py", line 720, in next
item = self._items.popleft()

during handling of the above exception, another exception occurred:

traceback (most recent call last):
file "/usr/local/lib/python3.6/multiprocessing/pool.py", line 726, in next
item = self._items.popleft()
indexerror: pop from an empty deque

during handling of the above exception, another exception occurred:

traceback (most recent call last):
file "/scancode-toolkit/bin/scancode", line 33, in
sys.exit(load_entry_point('scancode-toolkit', 'console_scripts', 'scancode')())
file "/scancode-toolkit/lib/python3.6/site-packages/click/core.py", line 722, in __call__
return self.main(*args, **kwargs)
file "/scancode-toolkit/lib/python3.6/site-packages/commoncode/cliutils.py", line 87, in main
**extra,
file "/scancode-toolkit/lib/python3.6/site-packages/click/core.py", line 697, in main
rv = self.invoke(ctx)
file "/scancode-toolkit/lib/python3.6/site-packages/click/core.py", line 895, in invoke
return ctx.invoke(self.callback, **ctx.params)
file "/scancode-toolkit/lib/python3.6/site-packages/click/core.py", line 535, in invoke
return callback(*args, **kwargs)
file "/scancode-toolkit/lib/python3.6/site-packages/click/decorators.py", line 17, in new_func
return f(get_current_context(), *args, **kwargs)
file "/scancode-toolkit/src/scancode/cli.py", line 421, in scancode
*args, **kwargs)
file "/scancode-toolkit/src/scancode/cli.py", line 815, in run_scan
quiet=quiet, verbose=verbose, kwargs=requested_options, echo_func=echo_func,
file "/scancode-toolkit/src/scancode/cli.py", line 1006, in run_scanners
with_timing=timing, progress_manager=progress_manager)
file "/scancode-toolkit/src/scancode/cli.py", line 1097, in scan_codebase
location, rid, scan_errors, scan_time, scan_result, scan_timings = next(scans)
file "/scancode-toolkit/lib/python3.6/site-packages/click/_termui_impl.py", line 259, in next
rv = next(self.iter)
file "/scancode-toolkit/src/scancode/pool.py", line 52, in wrap
return func(self, timeout=timeout or 3600)
file "/usr/local/lib/python3.6/multiprocessing/pool.py", line 730, in next
raise timeouterror
multiprocessing.context.timeouterror
```