Add __synch_synchronize function for arm

Fixes link failure when linking Ada programs on the raspberry pi

cpukit/score/cpu/arm/Makefile.am

@@ -27,6 +27,7 @@ libscorecpu_a_SOURCES += arm_exc_handler_high.c
 libscorecpu_a_SOURCES += arm-exception-frame-print.c
 libscorecpu_a_SOURCES += arm-exception-default.c
 libscorecpu_a_SOURCES += armv4-exception-default.S
+libscorecpu_a_SOURCES += armv4-sync-synchronize.c
 libscorecpu_a_SOURCES += armv7-thread-idle.c
 libscorecpu_a_SOURCES += armv7m-context-initialize.c
 libscorecpu_a_SOURCES += armv7m-context-restore.c

cpukit/score/cpu/arm/armv4-sync-synchronize.c

@@ -0,0 +1,9 @@
+void
+__sync_synchronize (void)
+{
+#ifdef ARM_MULTILIB_HAS_BARRIER_INSTRUCTIONS
+  asm volatile("dmb" : : : "memory");
+#else
+  asm volatile("" : : : "memory");
+#endif
+}