config.if: If gcc_version is already set, just use it.

config.if: If gcc_version is already set, just use it.

* config.if: If gcc_version is already set, just use it.  Don't set
gcc_version_trigger if it's already set, otherwise set it to
gcc/version.c, but only if the file exists.  If it is not set and
gcc/version.c does not exist, try to extract the version number from
$CC.

From-SVN: r62131