website: properly handle the dot dependency.

This was broken by the commit 388c0ef3d0
("website: add history page of the GNU Boot git repositories.").

Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
Acked-by: Adrien Bourmault <neox@gnu.org>

website/Makefile.am

@@ -27,8 +27,21 @@ endif
 index.html: index.html.tmpl
 	sed -e "s#WEBSITE_PREFIX#$(WEBSITE_PREFIX)#g" "$^" > "$@"
 
+if WANT_GUIX
+history/git-history.jpg: history/git-history.dot
+	guix time-machine \
+	--commit=$(GUIX_REVISION) \
+	-- \
+	shell \
+		--system=i686-linux \
+		--container \
+		graphviz \
+	-- \
+	dot -T jpg history/git-history.dot > "$@"
+else
 history/git-history.jpg: history/git-history.dot
 	dot -T jpg history/git-history.dot > "$@"
+endif
 
 # We need force the regeneration of the page because if only the git
 # commit changes, there is no way to know about it. In addition the

website/configure.ac

@@ -130,6 +130,11 @@ AS_IF([test x"$guix" = x"yes"],
              [AC_MSG_ERROR(
               [date was not found in PATH ($PATH)])])
 
+       AC_CHECK_PROG([FOUND_DOT], [dot], [dot])
+       AS_IF([test x"$FOUND_DOT" = x""],
+             [AC_MSG_ERROR(
+              [dot was not found in PATH ($PATH)])])
+
        AC_CHECK_PROG([FOUND_FIND], [find], [find])
        AS_IF([test x"$FOUND_FIND" = x""],
              [AC_MSG_ERROR(