Handle host_cpu of x86_64 like other x86s.

diff --git a/configure b/configure
index 0e1435c..e6d78e3 100755
--- a/configure
+++ b/configure
@@ -1487,6 +1487,7 @@
       test -n "$CC" || CC="gcc -m32"
       test -n "$LD" || LD="ld -m elf_i386"
       test -n "$AS" || AS="as --32"
+      host_cpu="i386"
     fi
     ;;
 esac