arch linux based dockerfile

[pattakosn]

• dockerfile with which I got the dependencies that are not available from arch linux repositories so that i can build on linux
• added changes in configuration scripts to copy these artifacts from the docker container to the local build env
• some fixes of the current python configuration scripts
• modify premake config to find these header/libs
• github linux builders

Please note that in my dockerfile, i am not using the usual FreeImage package but this one https://github.com/danoli3/FreeImage.git

[pattakosn]

with this branch, one should be able to run the generate_gmake2_vulkan script for a makefile build.
It is assumed that the following are installed on the host system

• premake5
• 7z
• docker
• SDL3
• assimp
• bullet
• renderdoc
• openimagedenoise

given these, there are the following commits:

• 1 commit with indentation fixes
• 1 commit of a dockerfile that downloads/builds compressonator, DirectXShaderCompiler and FreeImage.These are the dependencies that are not found in arch repositories. The github.com/danoli3/FreeImage fork of FreeImage was used instead of the one in sourceforge as it seems more active. The commands and the patch file required to build the original FreeImage lib are also included if one wants to switch back to it.
• 1 commit fixing generate_project_files. Specifically it modifies the script to use premake5 and 7z from the host system on linux
• 1 commit modifying generate_project_files to use the dockerfile to copy the compressonator, DXShaderCompiler and FreeImage built with the dockerfile in third_party/linux.
• 1 commit modifying premake.lua to find all required dependencies on linux

[pattakosn]

Note 0:
This PR combined with the linux fixes PR should provide a linux environment which builds Spartan. At least on my system I can use premake to compile it.

Note 1:
The included dockerfile whould also work with visual studio code for dockerized builds. ie to build spartan on a linux system without installing any dependencies on the host linux system. i haven't tested that much though

[pattakosn]

i rebased to the latest master. There were some build errors which i fixed in the added commits.
On my system, installing the requirements i mentioned before (using the package manager) and running the updated scripts i can use premake to build spartan.