use runtime.GOOS to determine architecture of container build for darwin

Fixes #28

Signed-off-by: chaosinthecrd <tom@tmlabs.co.uk>

Author: ChaosInTheCRD

mkctr.go

@@ -170,13 +170,9 @@ func canRunLocal(p v1.Platform) bool {
 	if p.OS != "linux" {
 		return false
 	}
-	if runtime.GOOS == "linux" {
+	if runtime.GOOS == "linux" || runtime.GOOS == "darwin" {
 		return p.Architecture == runtime.GOARCH
 	}
-	if runtime.GOOS == "darwin" {
-		// macOS can run amd64 linux binaries in docker.
-		return p.Architecture == "amd64"
-	}
 	return false
 }