Makefile:32: *** Warning: GLUON_BRANCH has been deprecated, please set GLUON_AUTOUPDATER_BRANCH and GLUON_AUTOUPDATER_ENABLED instead.

So let's use the new variables now.

After we can now build with BROKEN, the build for raspi4 should work.

People asked for the Raspberry Pi 4, but it's currently broken and hence
is not build if one doesn't set BROKEN. Thus, allow us to set BROKEN for
some targets to allow these images to be built.

This reverts commit 0df9f251. The target
doesn't seem to be supported, the build failed:

  make[1]: Leaving directory '/builds/firmware/site-ffs/gluon/openwrt'
  Please set GLUON_TARGET to a valid target. Gluon supports the following targets:
   * ar71xx-generic
   * ar71xx-tiny
   * ar71xx-nand
   * ath79-generic
   * brcm2708-bcm2708
   * brcm2708-bcm2709
   * ipq40xx-generic
   * ipq806x-generic
   * lantiq-xrx200
   * lantiq-xway
   * mpc85xx-generic
   * mpc85xx-p1020
   * ramips-mt7620
   * ramips-mt7621
   * ramips-mt76x8
   * ramips-rt305x
   * sunxi-cortexa7
   * x86-generic
   * x86-geode
   * x86-legacy
   * x86-64
  Makefile:158: recipe for target 'config' failed

This makes the gluon build fail since v2018.2.1