glibc: fixup retaining bootstrap-tools reference

https://github.com/NixOS/nixpkgs/pull/15867#issuecomment-227949096

pkgs/development/libraries/glibc/default.nix

@@ -72,6 +72,14 @@ in
       # Get rid of more unnecessary stuff.
       rm -rf $out/var $out/sbin/sln
 
+      # For some reason these aren't stripped otherwise and retain reference
+      # to bootstrap-tools; on cross-arm this stripping would break objects.
+      if [ -z "$crossConfig" ]; then
+        for i in "$out"/lib/*.a; do
+            strip -S "$i"
+        done
+      fi
+
       # Put libraries for static linking in a separate output.  Note
       # that libc_nonshared.a and libpthread_nonshared.a are required
       # for dynamically-linked applications.