ruby-runner.c: show the failed path

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63983 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ruby-runner.c

@@ -1,4 +1,5 @@
 #define _POSIX_C_SOURCE 200809L
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -73,5 +74,6 @@ main(int argc, char **argv)
     memcpy(p, rubyname, namesize);
 
     execv(rubypath, argv);
+    perror(rubypath);
     return -1;
 }