Using O_NONBLOCK for Linux as well

Sources/SwiftSerial/SerialPort.swift

@@ -42,7 +42,7 @@ public class SerialPort {
 		}
 
 		#if os(Linux)
-		fileDescriptor = open(path, readWriteParam | O_NOCTTY)
+		fileDescriptor = open(path, readWriteParam | O_NOCTTY | O_NONBLOCK)
 		#elseif os(OSX)
 		fileDescriptor = open(path, readWriteParam | O_NOCTTY | O_EXLOCK | O_NONBLOCK)
 		#endif