Pre_Scan ignore takes more than two minutes for 2000 files even with configuring more processes

### Description

The pre_scan ignore takes to much time to complete.
For 2000 files it takes more than two minute.
With 2000 files, the pre_scan should actually be finished quickly.
Which scales up if the scanned repository is even larger.
Checking the processes i noticed that the pre_scan ignore step does not use more than one process even though i specified 16.

### How To Reproduce
Scan a large repository like dotnet/runtime

`git clone https://github.com/dotnet/runtime.git`
`cd runtime`
`scancode -cli --strip-root --timeout 120 --ignore ** --processes 16 --verbose --license-references --json-pp /temp/result.json`

It will take a long time for scancode to finish. To speed it up, delete some files from the repository until you have about 2000 files left.
Now it took 134s to complete, but the scan itself only took 0.5s the rest was used by the pre-scan step.

### System configuration
OS: Windows
Scancode v.32.1.0
Installation Method: "Installation as an application"