Merge 'staging' into closure-size

This is mainly to get the update of bootstrap tools.
Otherwise there were mysterious segfaults:
https://github.com/NixOS/nixpkgs/pull/7701#issuecomment-203389817

pkgs/build-support/cc-wrapper/cc-wrapper.sh

@@ -46,9 +46,9 @@ while [ $n -lt ${#params[*]} ]; do
         isCpp=1
     elif [ "$p" = -nostdlib ]; then
         isCpp=-1
-    elif [ "${i:0:1}" != - ]; then
+    elif [ "${p:0:1}" != - ]; then
         nonFlagArgs=1
-    elif [ "$i" = -m32 ]; then
+    elif [ "$p" = -m32 ]; then
         if [ -e @out@/nix-support/dynamic-linker-m32 ]; then
             NIX_LDFLAGS="$NIX_LDFLAGS -dynamic-linker $(cat @out@/nix-support/dynamic-linker-m32)"
         fi