Fix error handling for command dotnet csharpier

[arg0d]

In Rust, command exit status has to be handled manually. Not handling exit status would cause the generator to generate invalid code when dotnet is installed, but csharpier is not installed.

Switch from using dotnet csharpier to using dotnet-csharpier. The former produces really verbose output by dotnet when csharpier is not installed or dotnet tools directory is not in PATH, while the latter returns a neat command not found error if CSharpier is not yet installed.

[arg0d]

@meenzen could you check if its fine to use dotnet-csharpier instead of dotnet csharpier.

[arg0d]

It seemed like error handling was adequate at first from CI run, but the errors were only handled when dotnet itself is not present in PATH.

The verbose output I'm talking about:

> dotnet csharpier
Could not execute because the specified command or file was not found.
Possible reasons for this include:
  * You misspelled a built-in dotnet command.
  * You intended to execute a .NET program, but dotnet-csharpier does not exist.
  * You intended to run a global tool, but a dotnet-prefixed executable with this name could not be found on the PATH.

[meenzen]

Calling the dotnet-csharpier command directly has slightly different behavior, it always calls the global-tool. If you have csharpier installed as a local tool (using a tool manifest) then the dotnet-csharpier command does not work.

Running dotnet csharpier will automatically choose the correct tool for the working directory.

I can't think of a better solution than using dotnet-csharpier in this case though, so this is a limitation we'll have to accept for now.

[arg0d]

If using dotnet-csharpier works for your current use case, then I'm inclined to merge this.

[meenzen]

I'm fine with that.

Obligatory LGTM