OK, following kanjitalk755's expert and generous advice, I've built rakslice's macemu-windows_build_script fork in Msys under Windows 7. I downloaded and installed a fresh copy of MinGW, added the mingw-developer-toolkit from the MinGW Installation Manager, and then (following the excellent guide on this site), created a directory named "src" in my MinGW\msys\1.0\home\MYUSERNAME\ folder.
As the guide says, I did this: downloaded the source code from:
http://www.libsdl.org/release/SDL-1.2.15.zip and extracted the folder inside the Zip to the src directory.
Then I downloaded a ZIP of rakslice's code from
https://github.com/rakslice/macemu/tree ... ild_script and extracted the folder inside the Zip to the src directory.
Then, from the Msys prompt, I did this:
cd src/SDL-1.2.15
./autogen.sh
./configure --disable-shared
make
make install
## when rebuilding SheepShaver after building SDL, skip the previous steps, but cd to SDL-1.2.15 and perform the next steps:
PATH=`pwd`/bin:$PATH
export PATH
cd ..
cd macemu-windows_build_script
cd SheepShaver
## next step (make links) not needed after first time
make links
cd src/Windows
## next step create symbolic link) not needed after first time
ln -s ../Unix/m4
NO_CONFIGURE=1 ../Unix/autogen.sh
./configure --with-gtk=no --disable-jit
## next step (edit sysdeps.h) not needed after first time
## delete sysdeps.h, line 28: #define min(x,y) ((x) < (y) ? (x) : (y))
## next step needed every time (unless you make matching edit in makefile.in)
## delete from makefile, line 40, the string "-lpthread"
make
strip SheepShaver.exe
and I had a working build, exactly as kanjitalk755 said.
Now, is it possible to do something similar with more up-to-date branches of the macemu code?
Again, thanks to kanjitalk755 for all his help.