[Lkw] how to build your own qemu

[Christoph Hellwig]

A few people had no working qemu, or a qemu where networking did not work
at all (and not just git clone).

It is very important that qemu has support for libslirp, as that is the
default networking.  On Debian/Ubuntu this done by:

	sudo apt-get install libslirp-dev

for other distributions it might work a little different.

There are some of the other required dependencies to build qemu on
Ubuntu from Rodrigo:

        sudo apt install libglib2.0-dev libfdt-dev libpixman-1-dev zlib1g-dev libaio-dev libusb-1.0-0-dev libspice-server-dev libnfs-dev libiscsi-dev liblzo2-dev libseccomp-dev libattr1-dev libcap-ng-dev ninja-build

then do:

git clone https://github.com/qemu/qemu
cd qemu
mkdir build
cd build
../configure --disable-werror --enable-slirp --target-list=x86_64-softmmu
--prefix=/opt/newqemu/
make
sudo make install

and use the already existing commented out line for the newqemu in the
kvm-jrsl.sh script.