nix: generate shell fix env flags.

pkgs/shell-generate.nix

@@ -34,12 +34,6 b' pkgs.stdenv.mkDerivation {'
     pkgs.aprutil
   ];
 
-  LC_ALL = "en_US.UTF-8";
-  LOCALE_ARCHIVE =
-    if pkgs.stdenv.isLinux
-    then "${pkgs.glibcLocales}/lib/locale/locale-archive"
-    else "";
-
   shellHook = ''
     runHook preShellHook
     echo "Setting SVN_* variables"
@@ -53,6 +47,8 b' pkgs.stdenv.mkDerivation {'
     # set unpack source date to 1980 to fix ZIP problems that does not support <1980
     export SOURCE_DATE_EPOCH=315532800
     export TMPDIR=/tmp
+    export LOCALE_ARCHIVE="${pkgs.glibcLocales}/lib/locale/locale-archive"
+    export LC_ALL="en_US.UTF-8"
 
     # Custom prompt to distinguish from other dev envs.
     export PS1="\n\[\033[1;32m\][pip2nix-generate-shell]$\[\033[0m\] "