As a note, the latest trunk on mingw gives me:

gcc -O2 -g -Wall -Wno-parentheses   -L.
-Wl,--stack,0x00200000,--enable-auto-import   main.o dmydln.o
dmyencoding.o miniprelude.o array.o bignum.o class.o compar.o
complex.o dir.o enum.o enumerator.o error.o eval.o load.o proc.o
file.o gc.o hash.o inits.o io.o marshal.o math.o numeric.o object.o
pack.o parse.o process.o random.o range.o rational.o re.o regcomp.o
regenc.o regerror.o regexec.o regparse.o regsyntax.o ruby.o safe.o
signal.o sprintf.o st.o strftime.o string.o struct.o time.o
transcode.o util.o variable.o version.o compile.o debug.o iseq.o vm.o
vm_dump.o thread.o cont.o ascii.o us_ascii.o unicode.o utf_8.o
newline.o fileblocks.o crypt.o flock.o lgamma_r.o strlcpy.o strlcat.o
win32.o  dmyext.o  -lshell32 -lws2_32   -o miniruby.exe



signal.o: In function `sig_trap':
C:/dev/downloads/ruby_snapshot/signal.c:698: undefined reference to
`register_sigaltstack'
signal.o: In function `Init_signal':
C:/dev/downloads/ruby_snapshot/signal.c:1106: undefined reference to
`register_sigaltstack'
collect2: ld returned 1 exit status
make: *** [miniruby.exe] Error 1

Thanks!
-=R