feat: add rust link a

__ffi/rust_link_a/hello.c

@@ -0,0 +1,11 @@
+#include <stdio.h>
+#include "hello.h"
+
+void print_line(const char* str) {
+  for (int i = 0; str[i] != 0; i++) {
+    char c = str[i];
+    printf("PUT:%d - %c\n", c, c);
+  }
+  // str++;
+  printf("puts:%s\n", str);
+}