Bug#1104177: libc++-18-dev fails to coinstall

[Simon McVittie]

Control: found -1 1:18.1.8-17

On Sat, 26 Apr 2025 at 15:34:17 +0200, Helmut Grohne wrote:
>libc++-18-dev explicitly declares the ability to coinstall via
>Multi-Arch: same. Attempting to do this practically fails though.
>
>$ mmdebstrap --variant=essential --verbose unstable /dev/null --architectures=amd64,i386 --include=libc++-18-dev,libc++-18-dev:i386

This is reproducible in testing (replace unstable by trixie in the sample 
mmdebstrap command-line) so there's no need for it to prevent the 
unrelated RC bug fix in 1:18.1.8-18 from migrating.

     smcv