When the build configuration changes and Makefiles are recreated, the
src/debug/Makefile and src/debug/*/Makefile files are not recreated,
because they're not managed in the usual way by automake. This can lead
to build failures or surprising inconsistencies between the main and
debug versions of the library when doing incremental builds.

This causes them to be regenerated if any of the corresponding non-debug
makefiles is newer.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	* src/Makefile.am (stamp-debug): Add all Makefiles as
	prerequisites.
	* src/Makefile.in: Regenerate.

Tested x86_64-linux. Committed to trunk.