make reconfigure broken (jdk8u only)

Backport to jdk8u

changeset:   2163:2209644bcac4   
user:        kevinw
date:        2018-04-10 07:46 -0700
8034199: Add 'reconfigure' target for re-creating a configuration
Reviewed-by: ihse, erikj, tbell

fails when there are more than one configure flags

( rm -rf build; set -x; bash configure --with-toolchain-type=gcc  --with-boot-jdk=$HOME/jdk/jdk7 && make reconfigure )
=>configure: Toolchain type gcc --with-boot-jdk=.../jdk/jdk7 is not valid on this platform.configure: Valid toolchains: gcc clang.