anchor.diff:  { stdenv
   , fetchurl
  +, lib
   
   , staticSupport ? false
   }:
  
positive.code: 
    NIX_CFLAGS_COMPILE = optional (!staticSupport) "-fPIC";
  
    preInstall = "mkdir -pv $out/{bin,lib,man/man1,man/man3,include/gsm}";
  
    meta = with stdenv.lib; {
      description = "Lossy speech compression codec";
      homepage = http://www.quut.com/gsm/;
      license = licenses.bsd2;
  
negative.code: in
  
  stdenv.mkDerivation rec {
    name = "gsm-1.0.16";
  
    src = fetchurl {
      url = "http://www.quut.com/gsm/${name}.tar.gz";
      multihash = "QmRfJYdFiqexpN9ob1CScLZFE2mQit1JaTvR3VSPr31iqj";
      sha256 = "725a3768a1e23ab8648b4df9d470aed38eb1635af3cbc8d0b64fef077236f4ce";
    };
  
    postPatch = /* Fix include directory */ ''
      sed -i Makefile \
        -e 's,$(GSM_INSTALL_ROOT)/inc,$(GSM_INSTALL_ROOT)/include/gsm,'
    '' + optionalString (!staticSupport) /* Build ELF shared object */ ''
      sed -i Makefile \
        -e 's,libgsm.a,libgsm.so,' \
        -e 's/$(AR) $(ARFLAGS) $(LIBGSM) $(GSM_OBJECTS)/$(LD) -shared -Wl,-soname,libgsm.so -o $(LIBGSM) $(GSM_OBJECTS) -lc/' \
        -e '/$(RANLIB) $(LIBGSM)/d'
    '';
  
    makeFlags = [
      "SHELL=${stdenv.shell}"
  