Bootstrapping and using --disable-libstdcxx will cause a build failure deep in compiling
stage2 so instead error out early in the toplevel configure so it is more user friendly.

Bootstrapped and tested on x86_64-linux-gnu.
Also made sure --disable-libstdcxx without --disable-bootstrap failed.

	PR bootstrap/105474

ChangeLog:

	* configure: Regenerate.
	* configure.ac: Error out if libstdc++ is not enabled
	with bootstrapping.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>