Check for error, warning, and message in vcpkg-configuration.json.

[BillyONeal]

$ type .\vcpkg-configuration.json
{
  "default-registry": { /* ... */ },
  "registries": [ /* ... */ ],
  "demands": {
    "example:hello": {
      "error": "example:hello matched"
    },
    "example:world and x86": {
      "error": "example:world & x86 matched"
    },
    "example:world and x64": {
      "error": "example:world & x64 matched"
    },
    "arm": {
      "error": "arm matched"
    }
  }
}
$ vcpkg activate --example hello
warning: vcpkg-artifacts are experimental and may change at any time.
ERROR: c:\Dev\test\vcpkg-configuration.json - example:hello matched
$ vcpkg activate --example world
warning: vcpkg-artifacts are experimental and may change at any time.
ERROR: c:\Dev\test\vcpkg-configuration.json - example:world & x64 matched
$ vcpkg activate --example world --x86
warning: vcpkg-artifacts are experimental and may change at any time.
ERROR: c:\Dev\test\vcpkg-configuration.json - example:world & x86 matched
$ vcpkg activate --arm
warning: vcpkg-artifacts are experimental and may change at any time.
ERROR: c:\Dev\test\vcpkg-configuration.json - arm matched

[vicroms]

This looks like something that should be tested, otherwise LGTM.

[BillyONeal]

I agree. Unfortunately we have no way to do e2e testing of artifacts right now or I would have added one.