https://github.com/termux/termux-packages/issues/15852

--- a/acinclude/ac_with_md5.m4
+++ b/acinclude/ac_with_md5.m4
@@ -26,7 +26,7 @@
 
     void md5_init (MD5CONTEXT *ctx);
 
-    main(int argc,char **argv) {
+    int main(int argc,char **argv) {
      #include "linkage.c"
      md5_init(NULL);
     }
