Cross-compiling for Windows on Ubuntu:

Install mingw packages from Ubuntu repositories. (I used mingw32-binutils, mingw32-runtime, and gcc-mingw32)

Download SDL-devel-1.2.14-mingw32.tar.gz from http://www.libsdl.org/download-1.2.php. Extract the contents of the subfolder SDL-1.2.14 of this archive into /usr/i586-mingw32msvc
Download bzip2-1.0.5-2-mingw32-dev.tar.gz and libbz2-1.0.5-2-mingw32-dll-2.tar.gz from mingw on Sourceforge. Extract these into /usr/i586-mingw32msvc


The compiler does not seem to like _inline or the #ifdef WIN32 version of x86_cpuid(). While adding #undef WIN32 somewhere is a tempting option, this messes up things like the path separator and stamps folder creation, and may harm compatibility with other compilers (I assume compatibility with other compilers was the original reason for using _inline?).

I chose to replace:
#ifdef WIN32
with:
#if defined(WIN32) && !defined(__MINGW32__)
for x86_cpuid() and where _inline is used, in the hope that this will work as before in other compilers like Visual Studio (I do not use it, so cannot test).


Compiling with make powder-sse3.exe and similar should then work. The resulting .exe needs the SDL.dll and libbz2-2.dll files from /usr/i586-mingw32msvc/bin in order to run.




Taliathion
I know nothing about macs or compiling for them, sorry.

antb
Line 600 ( below // interpolator, above mv = max(fabsf(..... )
Change to
#if defined(WIN32) && !defined(__MINGW32__)


For some strange reason 41.3 worked fine without this change....