libc: Fix wrong report from UBSan
```
ubsan_prologue: ================================================================================
ubsan_prologue: UBSAN: array-index-out-of-bounds in symtab/symtab_allsyms.c:62:37
__ubsan_handle_out_of_bounds: index 1619 is out of range for type 'symtab_s [1]'
ubsan_epilogue: ================================================================================
```
* Public Data
****************************************************************************/
-extern const struct symtab_s g_allsyms[1];
+extern const struct symtab_s g_allsyms[];
extern const int g_nallsyms;
/****************************************************************************
