anchor.diff:      "--${boolEn examplesSupport}-examples"
       "--disable-docs"
       #libc
  -    "--as=yasm"
  +    "--as=${if versionAtLeast source.version "1.6.2" then "nasm" else "yasm"}"
       "${if (sizeLimit != null) then "--size-limit=${sizeLimit}" else null}"
       "--disable-codec-srcs"
       "--disable-debug-libs"
  
positive.code:     # master
      "1.999" = {
        fetchzipversion = 3;
        version = "2017-09-27";
        rev = "c493ea1a6b7ade049ac22d8d063b73f12d65bbea";
        sha256 = "e3379632547091c9d162c0970619ae4c262c8364821439e1c3f1b592e1085e5e";
      };
    };
    source = sources."${channel}";
  
negative.code: , fetchFromGitHub
  , fetchurl
  , lib
  , nasm
  , perl
  , yasm
  
  