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.

#!/bin/sh
#
echo "Generating build information using autoconf"
echo "This may take a while ..."

# Generate SDL_revision.h
sh build-scripts/updaterev.sh

# Regenerate configuration files
cat acinclude/* >aclocal.m4
found=false
for autoconf in autoconf autoconf259 autoconf-2.59
do if which $autoconf >/dev/null 2>&1; then $autoconf && found=true; break; fi
done
if test x$found = xfalse; then
    echo "Couldn't find autoconf, aborting"
    exit 1
fi
(cd test; sh autogen.sh)

# Run configure for this platform
echo "Now you are ready to run ./configure"