Update ArPow local-onboarding guidance to include --work-tree option

[omajid]

https://github.com/dotnet/source-build/blob/main/Documentation/planning/arcade-powered-source-build/onboarding/local-onboarding.md#patching misses out on --work-tree option. We use that everywhere else. For example:

https://github.com/dotnet/installer/blob/74507010fafeb931a063f8649bff0b032ebc725b/src/SourceBuild/tarball/content/repos/Directory.Build.targets#L83

The option was originally added in #937 to allow tarball builds to work when it was extracted to a sub-directory of another (non-related) git repository.

For example, I see this error now manifesting as:

dotnet6.0/dotnet-1afc0b6892dcd718cd88e281f3acd840cb966a4d-x64-bootstrap/.dotnet/sdk/6.0.100-preview.6.21355.2/NuGet.targets(565,5): error : File 'dotnet6.0/dotnet-1afc0b6892dcd718cd88e281f3acd840cb966a4d-x64-bootstrap/src/nuget-client.7363366401b43f4ea250394db8dad3707e9a9636/NuGet.config' does not exist. [dotnet6.0/dotnet-1afc0b6892dcd718cd88e281f3acd840cb966a4d-x64-bootstrap/packages/restored/ArcadeBootstrapPackage/microsoft.dotnet.arcade.sdk/6.0.0-beta.21319.2/tools/Tools.proj]

Which looks impossible on first sight because https://github.com/NuGet/NuGet.Client/blob/7363366401b43f4ea250394db8dad3707e9a9636/eng/source-build-patches/0001-Rename-NuGet.Config-to-NuGet.config-to-account-for-a.patch was supposed to have renamed the file.

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[omajid]

I looked through the existing repositories and opened PRs against all repos that needed the --work-tree argument:

• [ArPow] Use --work-tree with git apply NuGet/NuGet.Client#4254
• [ArPow] Use --work-tree with git apply microsoft/vstest#3046
• [ArPow] Use --work-tree with git apply command-line-api#1401

With these fixes a local build of install works for me. Edit: still need similar patches for xliff-tasks and fsharp, but the source-build-patches have been integrated into main repo for those repos, so there's limited need for those in the longer term.

If/when we update to those SHAs in installer, we should get the fixes too. I can do backports to the release branches too, if someone can help me figure out which ones will be used by release/6.0.