fontforge: 20160404 -> 20170730 + support reproducible builds

pkgs/tools/misc/fontforge/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchFromGitHub, fetchpatch, lib
+{ stdenv, fetchFromGitHub, fetchpatch, lib, runCommand
 , autoconf, automake, gnum4, libtool, perl, gnulib, uthash, pkgconfig, gettext
 , python, freetype, zlib, glib, libungif, libpng, libjpeg, libtiff, libxml2, pango
 , withSpiro ? false, libspiro
@@ -9,22 +9,30 @@
 
 stdenv.mkDerivation rec {
   name = "fontforge-${version}";
-  version = "20160404";
+  version = "20170730";
+
+  # The way $version propagates to $version of .pe-scripts (https://github.com/dejavu-fonts/dejavu-fonts/blob/358190f/scripts/generate.pe#L19)
+  SOURCE_DATE_EPOCH = lib.fileContents (runCommand "unixtime-of-${version}" {} "date -d ${version} +%s > $out");
 
   src = fetchFromGitHub {
     owner = "fontforge";
     repo = "fontforge";
     rev = version;
-    sha256 = "15nacq84n9gvlzp3slpmfrrbh57kfb6lbdlc46i7aqgci4qv6fg0";
+    sha256 = "15k6x97383p8l40jvcivalhwgbbcdg5vciyjz6m9r0lrlnjqkv99";
   };
 
-  patches = [(fetchpatch {
-    name = "use-system-uthash.patch";
-    url = "http://pkgs.fedoraproject.org/cgit/fontforge.git/plain/"
-      + "fontforge-20140813-use-system-uthash.patch?id=8bdf933";
-    sha256 = "0n8i62qv2ygfii535rzp09vvjx4qf9zp5qq7qirrbzm1l9gykcjy";
-  })];
-  patchFlags = "-p0";
+  patches = [
+    ./fontforge-20140813-use-system-uthash.patch
+
+    (fetchpatch {
+       url = "https://github.com/fontforge/fontforge/compare/${version}...volth:rb-${version}.patch";
+       name = "fontforge-${version}-reproducible-build.patch";
+       sha256 = "089w94xnc0ik3rfx9b7q124x9n1nzbyzzcyynl1x31d22byxgl34";
+     })
+  ];
+
+  # do not use x87's 80-bit arithmetic, rouding errors result in very different font binaries
+  NIX_CFLAGS_COMPILE = lib.optionals stdenv.isi686 [ "-msse2" "-mfpmath=sse" ];
 
   buildInputs = [
     autoconf automake gnum4 libtool perl pkgconfig gettext uthash