Greg Jandl to SDL I did some digging, and I think I've found a better solution. By including some additional .m4 macros in the acinclude directory (http://www.gnu.org/software/autoconf-archive/ax_check_compiler_flags.html, http://www.gnu.org/software/autoconf-archive/ax_gcc_archflag.html and http://www.gnu.org/software/autoconf-archive/ax_gcc_x86_cpuid.html) then using the patch below (same as previous patch + one line change to configure.in), SDL will build correctly out of the box. The arch can then be overridden by --with-gcc-arch=<arch> (most will probably want to build with i686 there for general distribution) or --without-gcc-arch, to disable setting the arch all together. On my Atom netbook, I get -march=PentiumPro by default, which works great, as does --with-gcc-arch=i686.

##############################################################################
# ltversion.m4 -- version numbers			-*- Autoconf -*-
#
#   Copyright (C) 2004 Free Software Foundation, Inc.
#   Written by Scott James Remnant, 2004
#
# This file is free software; the Free Software Foundation gives
# unlimited permission to copy and/or distribute it, with or without
# modifications, as long as this notice is preserved.

# Generated from ltversion.in.

# serial 3012 ltversion.m4
# This file is part of GNU Libtool

m4_define([LT_PACKAGE_VERSION], [2.2.6])
m4_define([LT_PACKAGE_REVISION], [1.3012])

AC_DEFUN([LTVERSION_VERSION],
[macro_version='2.2.6'
macro_revision='1.3012'
_LT_DECL(, macro_version, 0, [Which release of libtool.m4 was used?])
_LT_DECL(, macro_revision, 0)
])