RFR: JDK-8256188: Adjust output of make/autoconf/configure

[Matthias Baesken]

The script make/autoconf/configure should give a bit more output in case various errors occur (e.g. missing autoconf).
The new output in case of missing autoconf adds the PATH; additionally we show on AIX some info on how to install autoconf.

bash /jdk_6/jdk/jdk/configure
Runnable configure script is not present
...
Autoconf is not found on the PATH (/opt/freeware/bin:/usr/bin:/etc:/usr/sbin), and AUTOCONF is not set.
You need autoconf to be able to generate a runnable configure script.
You might be able to fix this by installing autoconf from the 'AIX Toolbox for Linux Applications' (or compile it from the sources).
Error: Cannot find autoconf

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Commit messages:
 - JDK-8256188

Changes: https://git.openjdk.java.net/jdk/pull/1164/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1164&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256188
  Stats: 6 lines in 1 file changed: 3 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1164.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1164/head:pull/1164

PR: https://git.openjdk.java.net/jdk/pull/1164