firefox: Remove about:buildconfig

Storing the build configuration caused Firefox to retain a dependency
on gcc, glibc.dev and icu4c.dev.

This reduces the size of the firefox closure from 587 to 415 MiB.

pkgs/applications/networking/browsers/firefox/no-buildconfig.patch

@@ -0,0 +1,25 @@
+diff -ru -x '*~' firefox-55.0.3-orig/docshell/base/nsAboutRedirector.cpp firefox-55.0.3/docshell/base/nsAboutRedirector.cpp
+--- firefox-55.0.3-orig/docshell/base/nsAboutRedirector.cpp	2017-07-31 18:20:51.000000000 +0200
++++ firefox-55.0.3/docshell/base/nsAboutRedirector.cpp	2017-09-26 22:02:00.814151731 +0200
+@@ -40,10 +40,6 @@
+     nsIAboutModule::ALLOW_SCRIPT
+   },
+   {
+-    "buildconfig", "chrome://global/content/buildconfig.html",
+-    nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT
+-  },
+-  {
+     "checkerboard", "chrome://global/content/aboutCheckerboard.xhtml",
+     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+       nsIAboutModule::ALLOW_SCRIPT
+diff -ru -x '*~' firefox-55.0.3-orig/toolkit/content/jar.mn firefox-55.0.3/toolkit/content/jar.mn
+--- firefox-55.0.3-orig/toolkit/content/jar.mn	2017-07-31 18:20:52.000000000 +0200
++++ firefox-55.0.3/toolkit/content/jar.mn	2017-09-26 22:01:42.383350314 +0200
+@@ -40,7 +40,6 @@
+    content/global/plugins.css
+    content/global/browser-child.js
+    content/global/browser-content.js
+-*   content/global/buildconfig.html
+    content/global/contentAreaUtils.js
+ #ifndef MOZ_FENNEC
+    content/global/customizeToolbar.css

pkgs/applications/networking/browsers/firefox/packages.nix

@@ -12,10 +12,12 @@ rec {
       sha512 = "3cacc87b97871f3a8c5e97c17ef7025079cb5c81f32377d9402cdad45815ac6c4c4762c79187f1e477910161c2377c42d41de62a50b6741d5d7c1cd70e8c6416";
     };
 
-    patches = lib.optional stdenv.isi686 (fetchpatch {
+    patches =
-      url = "https://hg.mozilla.org/mozilla-central/raw-rev/15517c5a5d37";
+      [ ./no-buildconfig.patch ]
-      sha256 = "1ba487p3hk4w2w7qqfxgv1y57vp86b8g3xhav2j20qd3j3phbbn7";
+      ++ lib.optional stdenv.isi686 (fetchpatch {
-    });
+        url = "https://hg.mozilla.org/mozilla-central/raw-rev/15517c5a5d37";
+        sha256 = "1ba487p3hk4w2w7qqfxgv1y57vp86b8g3xhav2j20qd3j3phbbn7";
+      });
 
     meta = {
       description = "A web browser built from Firefox source tree";

pkgs/applications/networking/browsers/firefox/wrapper.nix

@@ -129,6 +129,8 @@ in stdenv.mkDerivation {
 
   passthru = { unwrapped = browser; };
 
+  disallowedRequisites = [ stdenv.cc ];
+
   meta = browser.meta // {
     description =
       browser.meta.description