-AC_CHECK_HEADERS([kcompat.h], [], [AC_MSG_ERROR([Cannot find kcompat headers (kcompat.h). Use [CFLAGS]=-Idir to specify their location.])])
+case "${host}" in
+changequote(,)dnl
+ i[34567]86-*-linux*)
+changequote([,])dnl
+ AC_CACHE_CHECK([if building for x86-64], [ust_cv_i386_is_x86_64],
+ [save_CPPFLAGS="$CPPFLAGS"
+ CPPFLAGS="$CPPFLAGS $CFLAGS"
+ AC_EGREP_CPP([got it], [
+#if __x86_64__
+got it
+#endif
+ ], [ust_cv_i386_is_x86_64=yes],
+ [ust_cv_i386_is_x86_64=no])
+ CPPFLAGS="$save_CPPFLAGS"])
+ ;;
+esac