fix: performance warning should not output ANSI codes if stderr redirected (apple#1059)

Author: iko1

Sources/ContainerCommands/Application.swift

@@ -91,7 +91,12 @@ public struct Application: AsyncParsableCommand {
 
         #if DEBUG
         let warning = "Running debug build. Performance may be degraded."
-        let formattedWarning = "\u{001B}[33mWarning!\u{001B}[0m \(warning)\n"
+        let formattedWarning: String
+        if isatty(FileHandle.standardError.fileDescriptor) == 1 {
+            formattedWarning = "\u{001B}[33mWarning!\u{001B}[0m \(warning)\n"
+        } else {
+            formattedWarning = "Warning! \(warning)\n"
+        }
         let warningData = Data(formattedWarning.utf8)
         FileHandle.standardError.write(warningData)
         #endif