Proj6014: Specify stable SDK version

A global.json file should only pin stable .NET SDK versions.

Pre-release SDKs (previews, release candidates) can contain unfinished features, changed behavior, and defects that are fixed only later on. Due to this, usage for production is strongly discouraged.

Non-compliant

global.json

{
  "sdk": {
    "version": "10.0.100-preview.4.25207.111"
  }
}

or

{
  "sdk": {
    "version": "10.0.401",
    "allowPrerelease": true
  }
}

or, without allowPrerelease for non-strict roll-forward policies (other than disable, patch or latestPatch):

{
  "sdk": {
    "version": "10.0.401",
    "rollForward": "latestMajor"
  }
}

Compliant

global.json

{
  "sdk": {
    "version": "10.0.401",
    "allowPrerelease": false
  }
}