$ grep "undefined symbols not allowed" logs/pkgs/*
cliquer-1.21.p4.log:libtool: link: warning: undefined symbols not allowed in x86_64-unknown-cygwin shared libraries
giac-1.5.0.87p0.log:libtool: warning: undefined symbols not allowed in x86_64-pc-cygwin shared libraries; building static only
libbraiding-1.0.p0.log:libtool: warning: undefined symbols not allowed in x86_64-unknown-cygwin shared libraries; building static only
rw-0.7.p0.log:libtool: link: warning: undefined symbols not allowed in x86_64-unknown-cygwin shared libraries
singular-4.1.1p2.p0.log:libtool: warning: undefined symbols not allowed in x86_64-unknown-cygwin shared libraries; building static only

Making all in gitfan
...
/usr/bin/bash ../../../libtool  --tag=CXX   --mode=link g++ -std=gnu++11  -O2 -g  -pipe -fno-common -g0 -O3 -Wno-unused-function -Wno-trigraphs -Wno-unused-parameter -Wunknown-pragmas -Wno-unused-variable -fomit-frame-pointer -fwrapv -fvisibility=default -finline-functions -fno-exceptions -fno-threadsafe-statics -fno-enforce-eh-specs -fconserve-space -funroll-loops -fno-delete-null-pointer-checks -fno-rtti -module -export-dynamic -avoid-version -flat_namespace -weak_reference_mismatches weak -undefined dynamic_lookup -L/cygdrive/d/a/sage/sage/local/lib -Wl,-rpath,/cygdrive/d/a/sage/sage/local/lib  -pipe -fno-common -g0 -O3 -Wno-unused-function -Wno-trigraphs -Wno-unused-parameter -Wunknown-pragmas -Wno-unused-variable -fomit-frame-pointer -fwrapv -fvisibility=default -finline-functions -fno-exceptions -fconserve-space -funroll-loops -fno-delete-null-pointer-checks  -Wl,-Bdynamic -o gitfan.la -rpath /cygdrive/d/a/sage/sage/local/libexec/singular/MOD gitfan_la-gitfan.lo  -lreadline -lncurses -lmpfr -lrt
libtool: warning: undefined symbols not allowed in x86_64-unknown-cygwin shared libraries; building static only
libtool: link: ar cru .libs/gitfan.a  gitfan_la-gitfan.o
libtool: link: ranlib .libs/gitfan.a
libtool: link: ( cd ".libs" && rm -f "gitfan.la" && ln -s "../gitfan.la" "gitfan.la" )

[meataxe-1.0.p0] /usr/bin/bash ../libtool  --tag=CC   --mode=link gcc  -g -O2  -L/opt/sagemath-9.0/local/lib -Wl,-rpath,/opt/sagemath-9.0/local/lib  -o libmtx.la -rpath /opt/sagemath-9.0/local/lib args.lo berlekmp.lo bsand.lo bscore.lo bsdup.lo bsissub.lo bsmatch.lo bsminus.lo bsop.lo bsor.lo bsprint.lo bsread.lo bswrite.lo cfinfo.lo charpol.lo chbasis.lo error.lo ffio.lo fpcore.lo fpdup.lo fpmul.lo fpmul2.lo fpprint.lo gcd.lo genseed.lo grmaprow.lo grmatcore.lo grtable.lo homcomp.lo imatcore.lo imatread.lo imatwrite.lo init.lo intio.lo issub.lo isisom.lo kernel-0.lo ldiag.lo maddmul.lo mat2vec.lo matadd.lo matclean.lo matcmp.lo maketabF.lo matcopy.lo matcore.lo matcut.lo matdup.lo matech.lo matid.lo matins.lo matinv.lo matmul.lo matnull.lo matorder.lo matpivot.lo matprint.lo matpwr.lo matread.lo mattr.lo mattrace.lo matwrite.lo message.lo mfcore.lo mfread.lo mfreadlong.lo mfwrite.lo mfwritelong.lo minpol.lo mkendo.lo mmulscal.lo mraddgen.lo mrcore.lo mrread.lo mrtranspose.lo mrwrite.lo msclean.lo mscore.lo mtensor.lo mtxobj.lo os.lo permcmp.lo permcore.lo permdup.lo perminv.lo permmul.lo permorder.lo permprint.lo permpwr.lo permread.lo permwrite.lo poladd.lo polcmp.lo polcore.lo polderive.lo poldiv.lo poldup.lo polgcd.lo polmul.lo polprint.lo polread.lo polwrite.lo quotient.lo random.lo rdcfgen.lo saction.lo setcore.lo setinsert.lo settest.lo spinup.lo spinup2.lo split.lo stabpwr.lo stfcore.lo stfread.lo stfwrite.lo string.lo sumint.lo temap.lo tkinfo.lo vec2mat.lo wgen.lo window.lo zcleanrow.lo zcmprow.lo zgap.lo zpermrow.lo zzz2.lo
[meataxe-1.0.p0] libtool:   error: can't build x86_64-unknown-cygwin shared library unless -no-undefined is specified