Build errors when repo folder path has spaces

[ecraig12345]

Repro steps

1. Make a folder with a space in the name, such as D:\some folder
2. Clone the Fabric Git repo into that folder
3. cd into the folder and npm run build

There will be a build error about the path D:\some not existing.

(This was initially filed under #7442 but root cause investigation/fix was moved to this issue per @micahgodbolt's request.)

Investigation

One issue is with the way install-run-rush.js spawns Rush in a child process, and I have a fix for that at microsoft/rushstack#1003. This affects both Windows and Mac.

There's also some issue with either Fabric's build scripts or one of their dependencies--the failure to build set-version occurs during the Jest step, but I'm still working on figuring out why. This only affects Windows.

[ecraig12345]

Closing this since we're no longer using Rush.