ffmpeg: small refactor (#437595)

  perl,

  texinfo,

  texinfo6,

  yasm,

  nasm,

  # You can fetch any upstream version using this derivation by specifying version and hash

  # NOTICE: Always use this argument to override the version. Do not use overrideAttrs.

  version, # ffmpeg ABI version. Also declare this if you're overriding the source.

  hash ? "", # hash of the upstream source for the given ABI version

  source ? fetchgit {

    url = "https://git.ffmpeg.org/ffmpeg.git";

    rev = "n${version}";

  source ? fetchFromGitea {

    domain = "code.ffmpeg.org";

    owner = "FFmpeg";

    repo = "FFmpeg";

    tag = "n${version}";

    inherit hash;

  },

  # instead.

  withFullDeps ? ffmpegVariant == "full",

  fetchgit,

  fetchFromGitea,

  fetchpatch2,

  # Feature flags

      perl

      pkg-config

    ]

    # 8.0 is only compatible with nasm, and we don't want to rebuild all older ffmpeg builds at this moment.

    ++ (if versionOlder version "8.0" then [ yasm ] else [ nasm ])

    ++ optionals stdenv.hostPlatform.isx86 [ nasm ]

    # Texinfo version 7.1 introduced breaking changes, which older versions of ffmpeg do not handle.

    ++ (if versionOlder version "5" then [ texinfo6 ] else [ texinfo ])

    ++ optionals withCudaLLVM [ clang ]