[docs, devscripts] Document `pyinst`'s argument passthrough (#5235)

Closes #4631
Authored by: jahway603

README.md

@@ -277,6 +277,8 @@ To build the standalone executable, you must have Python and `pyinstaller` (plus
 
 On some systems, you may need to use `py` or `python` instead of `python3`.
 
+`pyinst.py` accepts any arguments that can be passed to `pyinstaller`, such as `--onefile/-F` or `--onedir/-D`, which is further [documented here](https://pyinstaller.org/en/stable/usage.html#what-to-generate).
+
 Note that pyinstaller with versions below 4.4 [do not support](https://github.com/pyinstaller/pyinstaller#requirements-and-tested-platforms) Python installed from the Windows store without using a virtual environment.
 
 **Important**: Running `pyinstaller` directly **without** using `pyinst.py` is **not** officially supported. This may or may not work correctly.