Merge 'staging' into closure-size

- there were many easy merge conflicts
- cc-wrapper needed nontrivial changes

Many other problems might've been created by interaction of the branches,
but stdenv and a few other packages build fine now.

pkgs/os-specific/linux/libcap/default.nix

@@ -4,11 +4,11 @@ assert stdenv.isLinux;
 
 stdenv.mkDerivation rec {
   name = "libcap-${version}";
-  version = "2.22";
+  version = "2.24";
 
   src = fetchurl {
-    url = "mirror://gentoo/distfiles/${name}.tar.bz2";
-    sha256 = "03q50j6bg65cc501q87qh328ncav1i8qw2bjig99vxmmfx4bvsvk";
+    url = "mirror://kernel/linux/libs/security/linux-privs/libcap2/${name}.tar.xz";
+    sha256 = "0rbc9qbqs5bp9am9s9g83wxj5k4ixps2agy9dxr1v1fwg27mdr6f";
   };
 
   outputs = [ "dev" "out" ];