Make bails out when trying to reconfigure more than one configuration.

Example:

$ make reconfigure
No CONF given, but more than one configuration found in /localhome/pliden/openjdk/bugs/jdk9/hs-gc//build.
Available configurations:
* linux-x86-normal-server-fastdebug
* linux-x86_64-normal-server-fastdebug
Please retry building with CONF=<config pattern> (or SPEC=<specfile>)
Makefile:55: *** Cannot continue. Stop.
$ make reconfigure CONF=linux
Building target 'reconfigure' in the following configurations (matching CONF=linux):
* linux-x86-normal-server-fastdebug
* linux-x86_64-normal-server-fastdebug
make: *** No rule to make target `reconfigure'. Stop.

However, picking a single configuration works:

$ make reconfigure CONF=linux-x86_64-normal-server-fastdebug
Building 'linux-x86_64-normal-server-fastdebug' (matching CONF=linux-x86_64-normal-server-fastdebug)
Re-running configure using arguments '--with-jobs=14 --disable-zip-debug-info --disable-ccache --disable-precompiled-headers --with-debug-level=fastdebug'
Running generated-configure.sh
configure: Configuration created at Tue Apr 29 12:28:27 CEST 2014.
configure: configure script generated at timestamp 1398196583.
checking for basename... /usr/bin/basename
checking for bash... /bin/bash
checking for cat... /bin/cat
checking for chmod... /bin/chmod
[...]

but It would be nice to be able to reconfigure more than one configuration using CONF=<pattern>