hostinfo: report when running in Docker Desktop.

Signed-off-by: Denton Gentry <dgentry@tailscale.com>

hostinfo/hostinfo.go

@@ -87,6 +87,7 @@ const (
 	AWSFargate      = EnvType("fg")
 	FlyDotIo        = EnvType("fly")
 	Kubernetes      = EnvType("k8s")
+	DockerDesktop   = EnvType("dde")
 )
 
 var envType atomic.Value // of EnvType
@@ -144,6 +145,9 @@ func getEnvType() EnvType {
 	if inKubernetes() {
 		return Kubernetes
 	}
+	if inDockerDesktop() {
+		return DockerDesktop
+	}
 	return ""
 }
 
@@ -228,6 +232,13 @@ func inKubernetes() bool {
 	return false
 }
 
+func inDockerDesktop() bool {
+	if os.Getenv("TS_HOST_ENV") == "dde" {
+		return true
+	}
+	return false
+}
+
 type etcAptSrcResult struct {
 	mod      time.Time
 	disabled bool