Add dotnet-local scripts to make using in tree dotnet easier.

[jonpryor]

Using dotnet may require setting %PATH% to prefer bin\dotnet\dotnet over any other dotnet in %PATH%.

Usage:

# Unix
path/to/maui/dotnet-local.sh build App.sln

rem Windows
path\to\maui\dotnet-local.cmd build App.sln

If MAUI hasn't been built yet, an error message stating that build.sh or build.ps1 should be executed is printed.

[jonathanpeppers]

Overall these scripts are going to be useful in .NET 8, they dropped support for $DOTNET_HOST_PATH and $DOTNET_ROOT.

So, if you tried to run ./bin/dotnet/dotnet build someproject.sproj, the <Csc/> task might pick up a different dotnet and the build will fail.

[jonathanpeppers]

/cc @PureWeen I'm not sure we use those build.ps1/sh scripts or are they are vestigial? I think we could just say, "you need to build MAUI first" and link to:

https://github.com/dotnet/maui/blob/main/.github/DEVELOPMENT.md

[jonpryor]

On the one hand, sure, but on the other hand… I find that .github/DEVELOPMENT.md page to be inscrutable. How should I build dotnet/maui if I don't use build.sh/build.ps1?

And if build.sh/build.ps1 shouldn't be used, shouldn't we just delete them?

[jonathanpeppers]

Yes, I don't know why they exist if DEVELOPMENT.md doesn't mention them?

[PureWeen]

We were using build.sh and build.ps1 before dotnet had a cake tool and before anyone that didn't work here could even hope to build MAUI.

We could probably just delete them at this point

[jonpryor]

@jonathanpeppers wrote:

Overall these scripts are going to be useful in .NET 8, they dropped support for $DOTNET_HOST_PATH and $DOTNET_ROOT.

One issue with this comment is that I don't see anything "contributor-facing" within dotnet/maui which uses DOTNET_HOST_PATH or DOTNET_ROOT (unless eng/package.ps1 is supposed to be "contributor-facing"?).

What I do know is that if $PATH doesn't have the used dotnet first, "weird things" happen. Unfortunately, I don't recall what those "weird things" were, at least in terms of error messages or behavior, just that "the Csc task might use the system dotnet install, which doesn't work as expected with the local install", which isn't particularly actionable.

[jonpryor]

@PureWeen , @jonathanpeppers: error message has been updated.

[jonathanpeppers]

The scripts themselves look good now. ./bin/dotnet/dotnet will not be useable without them on the net8.0 branch currently.

[PureWeen]

/rebase