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/development/perl-modules/generic/default.nix

@@ -13,6 +13,9 @@ perl.stdenv.mkDerivation (
     # Prevent CPAN downloads.
     PERL_AUTOINSTALL = "--skipdeps";
 
+    # Avoid creating perllocal.pod, which contains a timestamp
+    installTargets = "pure_install";
+
     # From http://wiki.cpantesters.org/wiki/CPANAuthorNotes: "allows
     # authors to skip certain tests (or include certain tests) when
     # the results are not being monitored by a human being."