Ninja not able to build single-threaded starting with 1.9.1

[andreeis]

The fix for #1958 was meant for msbuild only, not as a general rule to skip over "-j" when parallelJobs is set to 1. This breaks ninja which cannot build single-threaded with CMT extension anymore.

[mark-ulrich]

This was my fear when submitting the PR. So what is the best solution? Is it to add a new configuration option? I considered this when creating the fix, but I was/am not familiar enough with the codebase to do so. I would be happy to work on this if no one else is working on it at the moment.

[bobbrow]

@mark-ulrich If you are willing to help out with this, we would appreciate it.

[bobbrow]

The fix for this issue is available in 1.10 "pre-release". You can help us validate it by:

1. Opening the extensions panel in VS Code
2. Selecting the CMake Tools extension
3. Clicking the "Switch to Pre-release Version" button