This is same as upstream commit:

http://cgit.freedesktop.org/systemd/systemd/commit/?id=d8d4bee76cf3b40ea923bc57d44aa0815ca9b5ff

Except we patch configure and config.h.in to avoid autotools.

--- src/udev/udev-builtin.c
+++ src/udev/udev-builtin.c
@@ -34,7 +34,7 @@ static const struct udev_builtin *builtins[] = {
         [UDEV_BUILTIN_BLKID] = &udev_builtin_blkid,
 #endif
         [UDEV_BUILTIN_BTRFS] = &udev_builtin_btrfs,
-#ifdef ENABLE_FIRMWARE
+#ifdef HAVE_FIRMWARE
         [UDEV_BUILTIN_FIRMWARE] = &udev_builtin_firmware,
 #endif
         [UDEV_BUILTIN_HWDB] = &udev_builtin_hwdb,
--- src/udev/udev.h
+++ src/udev/udev.h
@@ -140,7 +140,7 @@ enum udev_builtin_cmd {
         UDEV_BUILTIN_BLKID,
 #endif
         UDEV_BUILTIN_BTRFS,
-#ifdef ENABLE_FIRMWARE
+#ifdef HAVE_FIRMWARE
         UDEV_BUILTIN_FIRMWARE,
 #endif
         UDEV_BUILTIN_HWDB,
@@ -169,7 +169,7 @@ struct udev_builtin {
 extern const struct udev_builtin udev_builtin_blkid;
 #endif
 extern const struct udev_builtin udev_builtin_btrfs;
-#ifdef ENABLE_FIRMWARE
+#ifdef HAVE_FIRMWARE
 extern const struct udev_builtin udev_builtin_firmware;
 #endif
 extern const struct udev_builtin udev_builtin_hwdb;
--- src/udev/udevd.c
+++ src/udev/udevd.c
@@ -98,7 +98,7 @@ struct event {
         dev_t devnum;
         int ifindex;
         bool is_block;
-#ifdef ENABLE_FIRMWARE
+#ifdef HAVE_FIRMWARE
         bool nodelay;
 #endif
 };
@@ -444,7 +444,7 @@ static int event_queue_insert(struct udev_device *dev)
         event->devnum = udev_device_get_devnum(dev);
         event->is_block = streq("block", udev_device_get_subsystem(dev));
         event->ifindex = udev_device_get_ifindex(dev);
-#ifdef ENABLE_FIRMWARE
+#ifdef HAVE_FIRMWARE
         if (streq(udev_device_get_subsystem(dev), "firmware"))
                 event->nodelay = true;
 #endif
@@ -527,7 +527,7 @@ static bool is_devpath_busy(struct event *event)
                         return true;
                 }
 
-#ifdef ENABLE_FIRMWARE
+#ifdef HAVE_FIRMWARE
                 /* allow to bypass the dependency tracking */
                 if (event->nodelay)
                         continue;
--- configure
+++ configure
@@ -18066,6 +18099,11 @@
 done
 IFS=$OLD_IFS
 
+if test "x${FIRMWARE_PATH}" != "x"; then :
+
+$as_echo "#define HAVE_FIRMWARE 1" >>confdefs.h
+
+fi
  if test "x${FIRMWARE_PATH}" != "x"; then
   ENABLE_FIRMWARE_TRUE=
   ENABLE_FIRMWARE_FALSE='#'
--- config.h.in
+++ config.h.in
@@ -57,6 +57,9 @@
 /* Define to 1 if you have the <fcntl.h> header file. */
 #undef HAVE_FCNTL_H
 
+/* Define if FIRMWARE is available */
+#undef HAVE_FIRMWARE
+
 /* GCRYPT available */
 #undef HAVE_GCRYPT