RFR: JDK-8072732 Regression in configure due to JDK-8069057

[Magnus Ihse Bursie]

The fix for JDK-8069057 caused the configure script to respawn due to 
autoconf entry code. This causes all sorts of weird behaviour, 
especially when running “make reconfigure”.

We need to tell autoconf not to respawn, since we have already figured 
out the correct shell.

  * Bug: https://bugs.openjdk.java.net/browse/JDK-8072732
  *

    Patch inline:

    |diff --git a/common/autoconf/configure b/common/autoconf/configure
    --- a/common/autoconf/configure
    +++ b/common/autoconf/configure
    @@ -40,8 +40,9 @@
      echo "Error: This script must be run using bash." 1>&2
      exit 1
    fi
    -# Force autoconf to use bash
    +# Force autoconf to use bash. This also means we must disable autoconf re-exec.
    export CONFIG_SHELL=$BASH
    +export _as_can_reexec=no

    conf_script_dir="$TOPDIR/common/autoconf"
    |

/Magnus

​