The process is straightforward with a few pitfalls. First initialize the OpenEmbedded build environment:

git clone git://git.openembedded.org/openembedded-core oe-core
cd oe-core
git clone git://git.openembedded.org/bitbake bitbake
git checkout krogoth
cd bitbake
git checkout 1.30
cd ..
. ./oe-init-build-env
cd ../..

Now you should at the same level with oe-core. Clone the required layers:

git clone git://git.openembedded.org/bitbake
git clone git://git.openembedded.org/openembedded-core
git clone git://git.openembedded.org/meta-openembedded
git clone git://github.com/meta-qt5/meta-qt5.git
git clone git://git.openembedded.org/meta-xilinx
git clone https://github.com/Xilinx/meta-petalinux.git

Go to the build folder by cd oe-core/build. Modify the conf/bblayer.conf to something like

# LAYER_CONF_VERSION is increased each time build/conf/bblayers.conf
# changes incompatibly
LCONF_VERSION = "7"

BBPATH = "${TOPDIR}"
BBFILES ?= ""

BBLAYERS ?= " \
    <your top dir>/oe-core/meta \
    <your top dir>/meta-openembedded/meta-perl \
    <your top dir>/meta-openembedded/meta-systemd \
    <your top dir>/meta-openembedded/meta-gpe \
    <your top dir>/meta-openembedded/meta-python \
    <your top dir>/meta-openembedded/meta-efl \
    <your top dir>/meta-openembedded/meta-ruby \
    <your top dir>/meta-openembedded/meta-filesystems \
    <your top dir>/meta-openembedded/meta-gnome \
    <your top dir>/meta-openembedded/meta-multimedia \
    <your top dir>/meta-openembedded/meta-networking \
    <your top dir>/meta-openembedded/meta-webserver \
    <your top dir>/meta-openembedded/meta-xfce \
    <your top dir>/meta-openembedded/meta-initramfs \
    <your top dir>/meta-openembedded/meta-oe \
    <your top dir>/meta-qt5 \
    <your top dir>/oe-core/meta-selftest \
    <your top dir>/oe-core/meta-skeleton \
    <your top dir>/meta-xilinx \
    <your top dir>/meta-petalinux \
    "

Add these to the top of conf/local.conf:

PARALLEL_MAKE = "-j 8"
BB_NUMBER_THREADS = "8"
LICENSE_FLAGS_WHITELIST = "commercial"
MACHINE = "zedboard-zynq7"

Run bitbake core-image-minimal in the build directory. You should see the error:

ERROR: No recipes available for:
  xxx/oe-core/meta-xilinx/recipes-microblaze/gcc/gcc-source_6.%.bbappend
  xxx/oe-core/meta-xilinx/recipes-zynqmp/qemu/qemu_2.6%.bbappend
  xxx/oe-core/meta-petalinux/recipes-core/udev/udev_%.bbappend

The solution is simple: rm -rf the recipes :)

rm -rf xxx/oe-core/meta-xilinx/recipes-microblaze/gcc
rm -rf xxx/oe-core/meta-xilinx/recipes-zynqmp/qemu
rm -rf xxx/oe-core/meta-petalinux/recipes-core/udev

And now you can run BitBake to build the image:

bitbake core-image-minimal

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