[liba] Define __aeabi_atexit

Change-Id: Ibf8d2f5453d457d62989e0adcc070ae09e1c9074

liba/Makefile

@@ -56,6 +56,7 @@ tests += $(addprefix liba/test/, \
 # The use of aeabi-rt could be made conditional to an AEABI target.
 # In practice we're always using liba on such a target.
 objs += $(addprefix liba/src/aeabi-rt/, \
+  atexit.o \
   memclr.o \
   memcpy.o \
 )

liba/src/aeabi-rt/atexit.c

@@ -0,0 +1,7 @@
+/* See the "Run-time ABI for the ARM Architecture", Section 4.4.5 */
+
+int __cxa_atexit(void (* dtor)(void * this), void * object, void * handle);
+
+int  __aeabi_atexit(void * object, void (*destroyer)(void *), void * dso_handle) {
+  return __cxa_atexit(destroyer, object, dso_handle);
+}