Revert "Remove unnecessary AM_MAKEINFOFLAGS tweak"

This reverts commit 1a20a3f7ee.

It turns out that `texi2dvi` _does_ require `-I $(srcdir)` for
`@verbatiminclude default-ignore-list` to work after all.  It's needed
not for a normal docs build, but when `make distcheck` is run,
presumably because `distcheck` runs from a different directory.

Makefile.am

@@ -33,6 +33,18 @@ pm_DATA = lib/Stow.pm
 pmstow_DATA = lib/Stow/Util.pm
 
 export TEXI2DVI_BUILD_MODE = clean
+AM_MAKEINFOFLAGS = -I $(srcdir)
+
+# We require this -I parameter to ensure that the include of the
+# default ignore list in the manual works correctly, even when the
+# manual is being built via make distcheck from a different directory.
+# Unfortunately this is the only way to do it:
+#
+#   https://lists.gnu.org/archive/html/bug-automake/2008-09/msg00040.html
+#
+# even though it annoyingly produces a warning with the -Wall option
+# to AM_INIT_AUTOMAKE which has to be silenced via -Wno-override.
+TEXI2DVI = texi2dvi $(AM_MAKEINFOFLAGS)
 
 DEFAULT_IGNORE_LIST = $(srcdir)/default-ignore-list
 

configure.ac

@@ -19,7 +19,8 @@ AC_INIT([stow], [2.3.2], [bug-stow@gnu.org])
 AC_PREREQ([2.61])
 AC_CONFIG_AUX_DIR([automake])
 # Unfortunately we have to disable warnings for overrides, because we
-# need to override the built-in `check-TESTS' rule.
+# need to override the built-in `check-TESTS' rule and also the TEXI2DVI
+# variable.
 AM_INIT_AUTOMAKE([-Wall -Werror -Wno-override dist-bzip2 foreign])
 AC_PROG_INSTALL