[Backtracing] Add missing void cast to the paths test.

We need to cast in order to call `free()`.

rdar://103071801

Author: al45tair

test/Runtime/Paths.cpp

@@ -97,7 +97,7 @@ int main(void) {
 
   printf("aux path: %s\n", auxPath ? auxPath : "<NULL>");
 
-  free(auxPath);
+  free((void *)auxPath);
 
   return 0;
 }