RFR: JDK-8024620 config.log does not end up in corresponding configuration

[Magnus Ihse Bursie]

Autoconf creates by default a config.log in the current directory. Our 
configure script moves this file to the directory created for the 
configuration (e.g. build/linux...etc).

A previous fix launching the generated configure file in a subshell made 
the move to fail, since the directory name was not available outside the 
subshell.

Webrev:
http://cr.openjdk.java.net/~ihse/JDK-8024620-move-config.log-to-configuration-dir/webrev.01

/Magnus