fix: add guard to custom startup scripts

Fixes #2819.

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

variants/STM32F0xx/F070CBT/startup_Mx00_f070xb.S

@@ -1,3 +1,4 @@
+#if defined(ARDUINO_MALYANM200_F070CB) || defined(ARDUINO_MALYANM300_F070CB)
 /**
   ******************************************************************************
   * @file      startup_stm32f070xb.s
@@ -300,3 +301,4 @@ g_pfnVectors:
   .thumb_set USB_IRQHandler,Default_Handler
 
 /************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
+#endif /* ARDUINO_MALYANM200_F070CB || ARDUINO_MALYANM300_F070CB */

variants/STM32F1xx/F103C8T_F103CB(T-U)/startup_M200_f103xb.S

@@ -1,3 +1,4 @@
+#if defined(ARDUINO_MALYANM200_F103CB)
 /**
   *************** (C) COPYRIGHT 2017 STMicroelectronics ************************
   * @file      startup_stm32f103xb.s
@@ -389,3 +390,5 @@ g_pfnVectors:
   .thumb_set USBWakeUp_IRQHandler,Default_Handler
 
 /************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
+
+#endif /* ARDUINO_MALYANM200_F103CB */