[ci] Fail build if any untracked files written in git tree

[jpobst]

Context: #9661

Building on #9661, we also shouldn't be writing build artifacts to the source tree.

Any files generated by the build should be placed in /bin or /obj folders rather than the source tree.

Violations fixed by putting the artifact in .gitignore.

Current violations:

Mac:

Untracked files:
  (use "git add <file>..." to include in what will be committed)
	src/native/CMakePresets.json

Linux:

Untracked files:
  (use "git add <file>..." to include in what will be committed)
	src/native/CMakePresets.json
	src/native/clr/host/generate-pinvoke-tables
	src/native/clr/host/pinvoke-tables.include.generated
	src/native/mono/pinvoke-override/generate-pinvoke-tables
	src/native/mono/pinvoke-override/pinvoke-tables.include.generated

Windows

Untracked files:
  (use "git add <file>..." to include in what will be committed)
	dotnet-install.ps1
	src/native/CMakePresets.json

[jonpryor]

@grendello: is it safe to ignore changes to these files?

[grendello]

Yes, perfectly safe