Scons: revert providing the number of logical processors as the number of maximum concurrent jobs to speed up builds by default

[LeonarddeR]

Link to issue number:

Reverts #13226

Summary of the issue:

While building NVDA with multiple jobs leads to faster build times, it also leads to scrambled output which can be quite annoying when debugging.

Description of how this pull request fixes the issue:

Disable multiple jobs by default but warn users to run with -jX to get a faster build if applicable.

Testing strategy:

Tested specifying several numbers of build jobs on the command line

Known issues with pull request:

None known

Change log entries:

included in pr

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English

[seanbudd]

Thanks @LeonarddeR , we are going with this approach