configure: require opt-in to autotools

Autotools is going away. Break the autotools build so that people are
guaranteed to notice before it is gone. If they have problems with Meson, they
can still use --enable-autotools to build with autotools, but we really want to
hear about any problems.
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

.gitlab-ci.yml

@@ -36,7 +36,7 @@ build-native-autotools:
   - export BUILDDIR="$(pwd)/build-$BUILD_ID"
   - mkdir "$BUILDDIR" "$PREFIX"
   - cd "$BUILDDIR"
-  - ../autogen.sh --prefix="$PREFIX" --disable-setuid-install --enable-xwayland --enable-x11-compositor --enable-drm-compositor --enable-wayland-compositor --enable-headless-compositor --enable-fbdev-compositor --enable-rdp-compositor --enable-screen-sharing --enable-vaapi-recorder --enable-simple-clients --enable-simple-egl-clients --enable-simple-dmabuf-drm-client --enable-simple-dmabuf-v4l-client --enable-clients --enable-resize-optimization --enable-weston-launch --enable-fullscreen-shell --enable-colord --enable-dbus --enable-systemd-login --enable-junit-xml --enable-ivi-shell --enable-wcap-tools --disable-libunwind --enable-demo-clients-install --enable-lcms --with-cairo=image --enable-remoting
+  - ../autogen.sh --prefix="$PREFIX" --disable-setuid-install --enable-xwayland --enable-x11-compositor --enable-drm-compositor --enable-wayland-compositor --enable-headless-compositor --enable-fbdev-compositor --enable-rdp-compositor --enable-screen-sharing --enable-vaapi-recorder --enable-simple-clients --enable-simple-egl-clients --enable-simple-dmabuf-drm-client --enable-simple-dmabuf-v4l-client --enable-clients --enable-resize-optimization --enable-weston-launch --enable-fullscreen-shell --enable-colord --enable-dbus --enable-systemd-login --enable-junit-xml --enable-ivi-shell --enable-wcap-tools --disable-libunwind --enable-demo-clients-install --enable-lcms --with-cairo=image --enable-remoting --enable-autotools
   - make all
   - make check
   - make install

Makefile.am

@@ -10,7 +10,7 @@ libweston_module_LTLIBRARIES =
 noinst_LTLIBRARIES =
 BUILT_SOURCES =
 
-AM_DISTCHECK_CONFIGURE_FLAGS = --disable-setuid-install
+AM_DISTCHECK_CONFIGURE_FLAGS = --disable-setuid-install --enable-autotools
 
 EXTRA_DIST = weston.ini.in ivi-shell/weston.ini.in
 

configure.ac

@@ -84,6 +84,21 @@ AC_PROG_SED
 LT_PREREQ([2.2])
 LT_INIT([disable-static])
 
+AC_ARG_ENABLE(autotools,
+	      AS_HELP_STRING([--enable-autotools],
+			     [Allow building with autotools]),,
+	      enable_autotools=no)
+if test "x$enable_autotools" = "xno"; then
+	AC_ERROR([
+	*** Autotools support will be removed after the 6.0.0 release ***
+
+	Please, try the Meson based build and report any problems you might have
+	with it. Instructions and references can be found in README.md.
+	If you still want to continue building with autotools,
+	use --enable-autotools configure option.
+	])
+fi
+
 AC_ARG_VAR([WESTON_NATIVE_BACKEND],
            [Set the native backend to use, if Weston is not running under Wayland nor X11. @<:@default=drm-backend.so@:>@])
 AC_ARG_VAR([WESTON_SHELL_CLIENT],