dotnetup crashes with malformed global.json in the current directory

[jjonescz]

Create global.json like the following:

{
    "sdk": {
        // "version": "10.0.100"
    }
}

Run dotnetup on WSL.
Observe:

Error: '/' is invalid after a value. Expected either ',', '}', or ']'. Path: $.sdk | LineNumber: 2 | BytePositionInLine: 8.

Not a very clear error, took me a while to figure out what's wrong.

dotnet itself can handle such global.json btw. But even if it was completely malformed, I'm not sure why dotnetup should be reading global.json from the current directory in the first place.

[lbussell]

@baronfel convert to issue?