rework ra build

src/portable/renesas/rusb2/rusb2_ra.h

@@ -31,9 +31,21 @@
 extern "C" {
 #endif
 
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstrict-prototypes"
+
+// extra push due to https://github.com/renesas/fsp/pull/278
+#pragma GCC diagnostic push
+#endif
+
 /* renesas fsp api */
 #include "bsp_api.h"
 
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
+
 #define RUSB2_REG_BASE (0x40090000)
 
 #if defined(__ICCARM__)