So with all the hassle over symlinks, there is a different issue stopping things on MinGW. This seems to be the exact same issue as Gem was having. You can see the environment of the build in the build log, if that's useful.
libtool: compile: gcc -DHAVE_CONFIG_H -I. -I.. -I/home/pd/auto-build/pd-extended/pd/src -g -O2 -mms-bitfields -MT 0x260x260x7e.lo -MD -MP -MF .deps/0x260x260x7e.Tpo -c 0x260x260x7e.c -o 0x260x260x7e.o >/dev/null 2>&1 mv -f .deps/0x260x260x7e.Tpo .deps/0x260x260x7e.Plo /bin/sh ../libtool --tag=CC --mode=link gcc -g -O2 -mms-bitfields -module -avoid-version -shared -shrext .dll -L/home/pd/auto-build/pd-extended/pd -L/home/pd/auto-build/pd-extended/pd/src -o 0x260x260x7e.la -rpath 0x260x260x7e.lo -lregex -lpd -lm -lgdi32 -luser32 -lkernel32 -lcoldname -lcrtdll libtool: link: only absolute run-paths are allowed
http://autobuild.puredata.info/auto-build/2011-09-30/logs/2011-09-30_03.31.0...
.hc