After trying to install prerequisits : E: Unable to locate package

[und3fined404]

I run sudo apt-get install cmake pkg-config python ocl-icd-dev libegl1-mesa-dev ocl-icd-opencl-dev libdrm-dev libxfixes-dev libxext-dev llvm-3.6-dev clang-3.6 libclang-3.6-dev libtinfo-dev libedit-dev zlib1g-dev

Output :

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Note, selecting 'librust-clang-sys-0+clang-3-6-dev' for regex 'clang-3.6'
Note, selecting 'librust-clang-sys-0.27.0+gte-clang-3-6-dev' for regex 'clang-3.6'
Note, selecting 'librust-clang-sys-0.27+gte-clang-3-6-dev' for regex 'clang-3.6'
Note, selecting 'librust-clang-sys-0+gte-clang-3-6-dev' for regex 'clang-3.6'
Note, selecting 'librust-clang-sys+clang-3-6-dev' for regex 'clang-3.6'
Note, selecting 'librust-clang-sys-0.27.0+clang-3-6-dev' for regex 'clang-3.6'
Note, selecting 'librust-clang-sys-0.27+clang-3-6-dev' for regex 'clang-3.6'
Note, selecting 'librust-clang-sys+gte-clang-3-6-dev' for regex 'clang-3.6'
Note, selecting 'librust-clang-sys-dev' instead of 'librust-clang-sys+gte-clang-3-6-dev'
Note, selecting 'librust-clang-sys-dev' instead of 'librust-clang-sys+clang-3-6-dev'
Note, selecting 'librust-clang-sys-dev' instead of 'librust-clang-sys-0+clang-3-6-dev'
Note, selecting 'librust-clang-sys-dev' instead of 'librust-clang-sys-0+gte-clang-3-6-dev'
Note, selecting 'librust-clang-sys-dev' instead of 'librust-clang-sys-0.27+clang-3-6-dev'
Note, selecting 'librust-clang-sys-dev' instead of 'librust-clang-sys-0.27+gte-clang-3-6-dev'
Note, selecting 'librust-clang-sys-dev' instead of 'librust-clang-sys-0.27.0+clang-3-6-dev'
Note, selecting 'librust-clang-sys-dev' instead of 'librust-clang-sys-0.27.0+gte-clang-3-6-dev'
E: Unable to locate package llvm-3.6-dev
E: Couldn't find any package by glob 'llvm-3.6-dev'
E: Couldn't find any package by regex 'llvm-3.6-dev'
E: Unable to locate package libclang-3.6-dev
E: Couldn't find any package by glob 'libclang-3.6-dev'
E: Couldn't find any package by regex 'libclang-3.6-dev'

[bastiple]

LLVM/Clang 3.6 is rather old and has been dropped from many repositories, that is why apt can't find those packages. Beignet hasn't been updated in quite a while, so the documentation can't call for newer versions of LLVM/Clang.
But from my experience, beignet should build fine with LLVM/Clang 7, or even with newer versions, if certain patches are applied. (See the Archlinux PKGBUILD for those patches)