Cygwin: Fix remaining packages to build shared libraries, using `AM_LDFLAGS=-no-undefined`

[mkoeppe]

Follow up from #29152, where it was noted that the resulting build logs (​https://github.com/mkoeppe/sage/suites/1285136303/artifacts/20016238) show the following remaining issues:

egret:~/Downloads/logs-commit-e41329adfa1f1e69653ba127d6460d2bd7aaaf00-cygwin-standard$ grep "undefined symbols not allowed" pkgs/*
pkgs/barvinok-0.41.1.log:libtool: warning: undefined symbols not allowed in x86_64-unknown-cygwin shared libraries; building static only
pkgs/e_antic-0.1.8.log:libtool: warning: undefined symbols not allowed in x86_64-pc-cygwin shared libraries; building static only
pkgs/isl-0.20.log:libtool: warning: undefined symbols not allowed in x86_64-unknown-cygwin shared libraries; building static only
pkgs/libbraiding-1.1.log:libtool: warning: undefined symbols not allowed in x86_64-pc-cygwin shared libraries; building static only
pkgs/polylib-5.22.5.log:libtool: link: warning: undefined symbols not allowed in x86_64-unknown-cygwin shared libraries
pkgs/singular-4.1.1p2.p0.log:libtool: warning: undefined symbols not allowed in x86_64-unknown-c

(libbraiding was supposed to be fixed by the upgrade in #29152)

Also:

 [p_group_cohomology-3.3.2]   libtool:   error: can't build x86_64-unknown-cygwin shared library unless -no-undefined is specified
  [mpfrcx-0.5]   libtool:   error: can't build x86_64-unknown-cygwin shared library unless -no-undefined is specified

(​https://github.com/mkoeppe/sage/runs/2145195319)

[mkoeppe]

Setting new milestone based on a cursory review of ticket status, priority, and last modification date.

[mkoeppe]

singular will be fixed by #25993