pstoedit: fix build on darwin, tidy (#405719)

pkgs/by-name/ps/pstoedit/package.nix

@@ -23,6 +23,11 @@ stdenv.mkDerivation rec {
     hash = "sha256-VYi0MtLGsq2YKLRJFepYE/+aOjMSpB+g3kw43ayd9y8=";
   };
 
+  postPatch = ''
+    # don't use gnu-isms like link.h on macos
+    substituteInPlace src/pstoedit.cpp --replace-fail '#ifndef _MSC_VER' '#if !defined(_MSC_VER) && !defined(__APPLE__)'
+  '';
+
   outputs = [
     "out"
     "dev"
@@ -45,12 +50,6 @@ stdenv.mkDerivation rec {
       libiconv
     ];
 
-  # '@LIBPNG_LDFLAGS@' is no longer substituted by autoconf (the code is commented out)
-  # so we need to remove it from the pkg-config file as well
-  preConfigure = ''
-    substituteInPlace config/pstoedit.pc.in --replace '@LIBPNG_LDFLAGS@' ""
-  '';
-
   postInstall = ''
     wrapProgram $out/bin/pstoedit \
       --prefix PATH : ${lib.makeBinPath [ ghostscript ]}