aarch64: Fix warning about unused function on iOS

src/aarch64/ffi.c

@@ -55,6 +55,14 @@ struct call_context
   UINT64 x[N_X_ARG_REG];
 };
 
+#if FFI_EXEC_TRAMPOLINE_TABLE
+
+#ifdef __MACH__
+#include <mach/vm_param.h>
+#endif
+
+#else
+
 #if defined (__clang__) && defined (__APPLE__)
 extern void sys_icache_invalidate (void *start, size_t len);
 #endif
@@ -71,12 +79,6 @@ ffi_clear_cache (void *start, void *end)
 #endif
 }
 
-#if FFI_EXEC_TRAMPOLINE_TABLE
-
-#ifdef __MACH__
-#include <mach/vm_param.h>
-#endif
-
 #endif
 
 /* A subroutine of is_vfp_type.  Given a structure type, return the type code