Teensy-LC doesn't support CTS, so disable its code

teensy3/serial1.c

 
 int serial_set_cts(uint8_t pin)
 {
+#if defined(KINETISK)
 	if (!(SIM_SCGC4 & SIM_SCGC4_UART0)) return 0;
 	if (pin == 18) {
 		CORE_PIN18_CONFIG = PORT_PCR_MUX(3) | PORT_PCR_PE; // weak pulldown
 	}
 	UART0_MODEM |= UART_MODEM_TXCTSE;
 	return 1;
+#else
+	return 0;
+#endif
 }
 
 void serial_putchar(uint32_t c)

teensy3/serial2.c

 
 int serial2_set_cts(uint8_t pin)
 {
+#if defined(KINETISK)
 	if (!(SIM_SCGC4 & SIM_SCGC4_UART1)) return 0;
 	if (pin == 23) {
 		CORE_PIN23_CONFIG = PORT_PCR_MUX(3) | PORT_PCR_PE; // weak pulldown
 	}
 	UART1_MODEM |= UART_MODEM_TXCTSE;
 	return 1;
+#else
+	return 0;
+#endif
 }
 
 void serial2_putchar(uint32_t c)

teensy3/serial3.c

 
 int serial3_set_cts(uint8_t pin)
 {
+#if defined(KINETISK)
 	if (!(SIM_SCGC4 & SIM_SCGC4_UART2)) return 0;
 	if (pin == 14) {
 		CORE_PIN14_CONFIG = PORT_PCR_MUX(3) | PORT_PCR_PE; // weak pulldown
 	}
 	UART2_MODEM |= UART_MODEM_TXCTSE;
 	return 1;
+#else
+	return 0;
+#endif
 }
 
 void serial3_putchar(uint32_t c)