scripts: unset CONFIG_SITE

Some distributions (eg. openSUSE 12.1) systematically export
the CONFIG_SITE environment variable to point to a custom
script setting misc paths for ./configure.

This can, and does, break when cross-compiling for architectures
that are not supported by this script.

The simple workaround is to unset this variable.
NB: buildroot has a similar fix:
http://git.buildroot.org/buildroot/commit/?id=12c9f7dd6dee9c6029b4f9a12d6aac1516911ab4

Reported-by: Trevor Woerner <twoerner@gmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
(transplanted from 21f4f28e60ec0342133086c9a51e7f0e5b181fb8)

diff -durN binutils-2.20.1.orig/ld/emulparams/elf_i386.sh binutils-2.20.1/ld/emulparams/elf_i386.sh

--- binutils-2.20.1.orig/ld/emulparams/elf_i386.sh	2009-07-29 16:59:23.000000000 +0200

+++ binutils-2.20.1/ld/emulparams/elf_i386.sh	2010-08-17 19:32:12.000000000 +0200

@@ -13,3 +13,13 @@

 NO_SMALL_DATA=yes

 SEPARATE_GOTPLT=12

 IREL_IN_PLT=

+

+# In Gentoo, we install 32bit libs into /lib32 in an

+# ABI setup with amd64/x86

+case "$target" in

+  x86_64*-linux*)

+    case "$EMULATION_NAME" in

+      *i386*) LIBPATH_SUFFIX=32  ;;

+    esac

+  ;;

+esac