Ignore certain compiler options on ARMCC

ARMCC also sets __GNU__ macro, but doesn't support
GCC diagnostic pragmas.

src/device/dcd.h

@@ -106,12 +106,12 @@ typedef struct TU_ATTR_ALIGNED(4)
 void dcd_init       (uint8_t rhport);
 
 // Interrupt Handler
-#if __GNUC__
+#if __GNUC__ && !defined(__ARMCC_VERSION)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wredundant-decls"
 #endif
 void dcd_int_handler(uint8_t rhport);
-#if __GNUC__
+#if __GNUC__ && !defined(__ARMCC_VERSION)
 #pragma GCC diagnostic pop
 #endif