Remove unused parameters from test code.

test/same-source-file-name/src/prog2.c

 #include <stdio.h>
 
 extern void func(void);
 
-int main(int argc, char *argv[])
+int main(void)
 {
   printf("Hello from prog2.c\n");
   func();
   /*
    * Uncomment to test same-named files in different directories,
    * which Visual Studio doesn't support.
   subdir1_func();
   subdir2_func();
    */
   return 0;
 }