BDW-GC, GMP, libffi, libunistring, Readline: Don't use the native `strip'.

Using the native `strip' breaks static libraries when cross-compiling.

svn path=/nixpkgs/trunk/; revision=27572

pkgs/development/libraries/libunistring/default.nix

@@ -55,4 +55,11 @@ stdenv.mkDerivation (rec {
 # can't find the dll, it will only create a static library.
 (if (stdenv ? glibc)
  then {}
- else { configureFlags = "--with-libiconv-prefix=${libiconv}"; }))
+ else { configureFlags = "--with-libiconv-prefix=${libiconv}"; })
+
+//
+
+# Don't run the native `strip' when cross-compiling.
+(if (stdenv ? cross)
+ then { dontStrip = true; }
+ else { }))