How does one make a bash "builtin" (shared loadable module) on cygwin

[Rocky Bernstein <rocky@gnu.org>]

 I am trying to build a bash "builtin" (a dynamically loadable bash
module) on cygwin. Here's the error message I get via automake/make:
$ make
gcc  -g -O2   -o set0.exe -shared set0-set0.o
set0-set0.o: In function `set0_builtin':
/tmp/bashdb/builtin/set0.c:46: undefined reference to `_builtin_error'
/tmp/bashdb/builtin/set0.c:47: undefined reference to `_builtin_usage'
/tmp/bashdb/builtin/set0.c:51: undefined reference to `_dollar_vars'
/tmp/bashdb/builtin/set0.c:52: undefined reference to `_xmalloc'
/tmp/bashdb/builtin/set0.c:52: undefined reference to `_dollar_vars'
/tmp/bashdb/builtin/set0.c:42: undefined reference to `_builtin_error'
/tmp/bashdb/builtin/set0.c:43: undefined reference to `_builtin_usage'
collect2: ld returned 1 exit status
make: *** [set0.exe] Error 1
The complete Makefile.am and code is listed at
http://bashdb.git.sourceforge.net/git/gitweb.cgi?p=bashdb/bashdb;a=tree;f=builtin;h=428fd8f3598c88eabb10b3ba800fb900da9f858c;hb=HEAD

Perhaps I need to tell cygwin that these symbols are supposed to be
undefined since they are part of bash?
I've tried looking at gcc documentation for linker options but it's
all a mystery to me.
Thanks in advance for help, suggestions or links to documentation.
Regards,
   rocky

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