Use the time stamp file technique recommended by the autoconf manual
to prevent unneccesary rebuilds because of an unchanged config.h.
Uses the automake trick of generating the stamp files in the
_AC_AM_CONFIG_HEADER_HOOK macro instead of littering the source
directory with stamp-h.in files.
Add an extra ./config.status run after ./config.status --recheck
because with --recheck it doesn't actually try to remake the generated
files (and thus doesn't make the timestamp files). Thus without the
extra run, each stamp-*-h target would need to independently run
./config.status to make sure it wasn't changed by the configuration
change.
An orthogonal fix of how config.status is called in subdirectories.
When in a subdirectory and config.status is called with
../config.status and $(srcdir) is a relative path, config.status gets
confused. Fixed by replacing '../config.status --file=Makefile.in'
with 'cd ..; ./config.status --file=<dir>/Makefile.in'
(cherry picked from commit 7ead2aa88b)
7eb4825435