busybox.inc: fix CONFIG_EXTRA_CFLAGS configmangle

With current busybox Kbuild, setting .config to:

  CONFIG_EXTRA_CFLAGS="foo" "bar"

and then running 'make oldconfig' results in .config containing:

  CONFIG_EXTRA_CFLAGS="foo"

ie the CONFIG_EXTRA_CFLAGS configmangle in the busybox.inc doesn't
currently work as intended. Remove the extra \" \" to ensure that
${HOST_CC_ARCH} gets added to CONFIG_EXTRA_CFLAGS.

(From OE-Core rev: 5f822373fadff2415cf1602b9d58fae0dbd33730)

Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/busybox/busybox.inc

@@ -96,7 +96,7 @@ python () {
                    ("\\n".join((d.expand("${OE_FEATURES}").split("\n")))))
   d.setVar('configmangle_append',
                  "/^### CROSS$/a\\\n%s\n" %
-                  ("\\n".join(["CONFIG_EXTRA_CFLAGS=\"${CFLAGS}\" \"${HOST_CC_ARCH}\""
+                  ("\\n".join(["CONFIG_EXTRA_CFLAGS=\"${CFLAGS} ${HOST_CC_ARCH}\""
                         ])
                   ))
 }