Improvements to build system

[nmoinvaz]

• Compile each zlib variant with pigz independently.
  • Each version of pigz is tied to its own unique zlib. It allows for easily debugging a specific version of pigz tied to a certain version of zlib. Before the build script would nuke each folder when it recompiled a new variant.
• Use mainline pigz repository.
  • Copy necessary files from pigz directory and then build.
  • We no longer have to use customized repositories with a CMake super build script.
  • These changes make this benchmark is more self-contained.
• Added rebuild and toolchain args to compile script.

I also removed a_compile_dynamic.py. I'm not sure exactly of the purpose of it, but it seemed confusing to have two build scripts. It seems like we can accomplish the same thing with a_compile.py but just add a another command line argument.

[neurolabusc]

@nmoinvaz this looks great. My intention has always been to use the mainline pigz repository. However, I want to build production ready versions of pigz for each operating system. The mainline pigz does not support non-Latin characters on the Windows operating system. I would suggest we defer merging your PR until @madler has had a chance to review the pigz pull request that provides full Windows support.

[nmoinvaz]

Closing this pull request. I have since added pigz-bench to zlib-ng organization which includes some of these improvements. Thank you!