--- Comment #5 from Thomas Plank <tplank at gmx dot at> ---
(In reply to Thomas Plank from comment #4)
> I'm pretty sure I already had binutils updated to 2.30.
> I will give it a try with a downgrade to 2.29.1 and check if gcc 7.3.0
> builds then.
I didn't do the downgrade but used the patched binutils version.
GCC now builds under cygwin, see below:
$ gcc -v
Using built-in specs.
Configured with: ../gcc-7.3.0/configure --enable-threads
--with-mpc=/usr/local --with-isl=/usr/local --with-mpfr=/usr/local
Thread model: posix
gcc version 7.3.0 (GCC)