build: Allow disabling the update of udev rules

We can only create the udev rules file when we're not cross-compiling,
so allow people to disable updating the file when building from
tarballs.

If you run with --enable-udev-rules=no and the
60-fprint-autosuspend.rules doesn't exist, you're on your own.

configure.ac

@@ -129,6 +129,16 @@ AC_SUBST(GLIB_LIBS)
 imagemagick_found=no
 gdkpixbuf_found=no
 
+AC_ARG_ENABLE(udev-rules,
+	AC_HELP_STRING([--enable-udev-rules],[Update the udev rules]),
+	[case "${enableval}" in
+	yes) ENABLE_UDEV_RULES=yes ;;
+	no) ENABLE_UDEV_RULES=no ;;
+	*) AC_MSG_ERROR(bad value ${enableval} for --enable-udev-rules) ;;
+	esac],
+	[ENABLE_UDEV_RULES=yes]) dnl Default value
+AM_CONDITIONAL(ENABLE_UDEV_RULES, test x$ENABLE_UDEV_RULES = "xyes")
+
 AC_ARG_WITH(udev-rules-dir,
 	    AS_HELP_STRING([--with-udev-rules-dir=DIR],[Installation path for udev rules @<:@auto@:>@]),
 	    [ac_with_udev_rules_dir=$withval],

libfprint/Makefile.am

@@ -81,8 +81,10 @@ fprint_list_udev_rules_LDADD = $(builddir)/libfprint.la
 
 udev_rules_DATA = 60-fprint-autosuspend.rules
 
+if ENABLE_UDEV_RULES
 $(udev_rules_DATA): fprint-list-udev-rules
 	$(builddir)/fprint-list-udev-rules > $@
+endif
 
 if ENABLE_UPEKE2
 DRIVER_SRC += $(UPEKE2_SRC)