ecm build failure on cygwin-minimal

[mkoeppe]

​https://github.com/mkoeppe/sage/runs/493864794

libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I./x86_64 -I/cygdrive/d/a/sage/sage/local/include -I/cygdrive/d/a/sage/sage/local/include -g -march=native -g -O3 -fPIC -c ecm.c  -DDLL_EXPORT -DPIC -o .libs/libecm_la-ecm.o
In file included from sp.h:33,
                 from ecm-impl.h:29,
                 from ecm.c:26:
ecm-gmp.h:134:8: warning: '__gmpn_redc_n' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
  134 |   void __gmpn_redc_n (mp_ptr, mp_ptr, mp_srcptr, mp_size_t, mp_srcptr);
      |        ^~~~~~~~~~~~~
/tmp/cco2lRak.s: Assembler messages:
/tmp/cco2lRak.s:1351: Error: invalid register for .seh_savexmm
/tmp/cco2lRak.s:1776: Error: invalid register for .seh_savexmm
make[6]: *** [Makefile:1085: libecm_la-ecm.lo] Error 1
make[6]: Leaving directory '/cygdrive/d/a/sage/sage/local/var/tmp/sage/build/ecm-7.0.4.p1/src'

[mkoeppe]

This failure seems to depend on the CPU where it gets to run. It built correctly on cygwin-minimal at ​https://github.com/mkoeppe/sage/runs/518106009

[mkoeppe]

Moving this ticket to 9.4, as it seems unlikely that it will be merged in 9.3, which is in the release candidate stage

[mkoeppe]

Stalled in needs_review or needs_info; likely won't make it into Sage 9.5.

[mkoeppe]

outdated

[klee]

I agree.