Hello,

I'm the maintainer of https://hub.docker.com/r/silex/emacs

Since a while, the docker images from "master" segfault:

```
philippe@pv-desktop:~$ docker run -it --rm silex/emacs:master
Fatal error 11: Segmentation fault
Backtrace:
emacs(+0x132cae)[0x555966f19cae]
emacs(+0x11925a)[0x555966f0025a]
emacs(+0x13107e)[0x555966f1807e]
emacs(+0x131328)[0x555966f18328]
emacs(+0x1313ac)[0x555966f183ac]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x12890)[0x7f3010977890]
```

The binary is semi-working tho, like for example:

```
philippe@pv-desktop:~$ docker run -it --rm silex/emacs:master emacs --version
GNU Emacs 27.0.50
Copyright (C) 2019 Free Software Foundation, Inc.
GNU Emacs comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of GNU Emacs
under the terms of the GNU General Public License.
For more information about these matters, see the file named COPYING.
```

Here attached you'll find the gdb trace and a strace log. I tried to build the image with debug flags using what's in DEBUG, but the errors are similar.

I know that recently the portable dumper branch was merged, I suspect it has to do with the segfault... If necessary, I can bisect to find the offending commit, but I was hoping someone would quickly know what is happening.

This happens even if I run the container in privileged mode.

Kind regards,
Philippe