RFR: 8193620: Update path to autogen.sh in log message

[Erik Helin]

Hi all,

while working a bit on the configure code I noticed that the error 
message when autoconf is missing prints the wrong path to autogen.sh. 
This tiny patch updates the error message:

diff -r 589a6f1d86e9 -r 3ba5af45725a make/autoconf/configure
--- a/make/autoconf/configure   Sat Dec 09 07:50:50 2017 -0800
+++ b/make/autoconf/configure   Fri Dec 15 13:55:46 2017 +0100
@@ -60,7 +60,7 @@
  run_autogen_or_fail() {
    if test "x`which autoconf 2> /dev/null | grep -v '^no autoconf in'`" 
= x; then
      echo "Cannot locate autoconf, unable to correct situation."
-    echo "Please install autoconf and run 'bash autogen.sh' to update 
the generated files."
+    echo "Please install autoconf and run 'bash 
$conf_script_dir/autogen.sh' to update the generated files."
      echo "Error: Cannot continue" 1>&2
      exit 1
    else

Bug:
https://bugs.openjdk.java.net/browse/JDK-8193620

Testing:
- Tested locally by uninstalling autconf, updating a configure file and 
verifying that error message is correct

Thanks,
Erik