bug#33709: Hang when compiled with --coverage and gcc 7.3

[Glenn Morris <rgm@gnu.org>]

Package: emacs
Version: 27.0.50

The Emacs hydra jobset at https://hydra.nixos.org/jobset/gnu/emacs-trunk
was recently updated to a more recent version of the Nix package
collection. Ever since then, the "coverage" job (which is the one that
runs "make check") has timed out after spending hours failing to
compiled the first test .el file.

I have reproduced the problem on RHEL 7.6 as follows:

bootstrap as normal
./make-dist --snapshot --no-check --no-changelog --no-compress
tar xvf ../emacs-27.0.50.tar
cd emacs-27.0.50

scl enable devtoolset-7  # this enables gcc 7.3.1 as the default compiler
export CFLAGS=--coverage
./configure --without-all --without-x --without-libgmp
make -j8

The build completes fine, but now eg:

./src/emacs --help

never exits. It prints the usage message, then hangs.