bsp,abstract-machine: fix the order of .rti_fn* sections

* now initcall can work successfully, and msh can show prompt

bsp/abstract-machine/src/init.c

@@ -1,6 +1,9 @@
 #include <am.h>
 #include <rtthread.h>
 
+void *__fsymtab_start = NULL;
+void *__fsymtab_end = NULL;
+
 #define RT_HW_HEAP_BEGIN heap.start
 #define RT_HW_HEAP_END heap.end
 

bsp/abstract-machine/src/libc.c

@@ -0,0 +1,9 @@
+#include <klib.h>
+
+char *strchr(const char *s, int c) {
+  assert(0);
+}
+
+char *strstr(const char *haystack, const char *needle) {
+  assert(0);
+}