Allows using up to date simde and newer compilers for small performance
improvements. Ubuntu 18 and 20 are EOL and Ubuntu 22 was released over four
years ago.
This will also hopefully allow us to build slang for the upcoming
transition to slang based shaders.
The upgrade was needed as I couldn't get Xenial to boot in the QEMU VM.
In any case Bionic is now three years old and comes with GLIBC 2.27
released on 2018-02-01 which will be almost four years old when the next
version of kitty is released.
