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: 
    nativeBuildInputs = [
      perl
      yasm
    ];
  
    postPatch = ''
      patchShebangs ./build/make/rtcd.pl
  
negative.code:     # master
      "1.999" = {
        fetchzipversion = 3;
        version = "2017-11-06";
        rev = "6fbc354c97ca45754a76674dba5f6b43c2b0c15a";
        sha256 = "ac4e1e85b286bf6f730de23656687cfede95c4127246d68d200c0a9dd098cfdd";
      };
    };
    source = sources."${channel}";
  