Error when installing "g++-multilib libc6-dev-i386" on 64 bit machine

[bel]

I'm a software developer. I tried to build for 32 bit Linux on 64 bit Linux, to check type cast warnings occurring only for 32 bit versions. But it seems I cannot build for 32 bit on my 64 bit machine - gcc -m32 will fail with "/usr/bin/ld: cannot find -lgcc".
Googled for a solution and found https://www.cyberciti.biz/tips/compile-32bit-application-using-gcc-64-bit-linux.html
Typed "sudo apt-get install g++-multilib libc6-dev-i386".

Then an error message popped up.

lsb_release -rd
Description: Ubuntu 16.04.2 LTS
Release: 16.04

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: libc6-dev-i386 (not installed)
ProcVersionSignature: Ubuntu 4.4.0-64.85-generic 4.4.44
Uname: Linux 4.4.0-64-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
Date: Sat Jul 29 20:19:44 2017
DpkgTerminalLog:
 Vorbereitung zum Entpacken von .../libc6-dev-i386_2.23-0ubuntu9_amd64.deb ...
 Entpacken von libc6-dev-i386 (2.23-0ubuntu9) ...
 dpkg: Fehler beim Bearbeiten des Archivs /var/cache/apt/archives/libc6-dev-i386_2.23-0ubuntu9_amd64.deb (--unpack):
  Versuch, »/usr/include/sys/uio.h« zu überschreiben, welches auch in Paket libc6-dev-amd64:i386 2.23-0ubuntu9 ist
ErrorMessage: Versuch, »/usr/include/sys/uio.h« zu überschreiben, welches auch in Paket libc6-dev-amd64:i386 2.23-0ubuntu9 ist
InstallationDate: Installed on 2014-11-24 (977 days ago)
InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Release amd64 (20141022.1)
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.1
 apt 1.2.19
SourcePackage: glibc
Title: package libc6-dev-i386 (not installed) failed to install/upgrade: Versuch, »/usr/include/sys/uio.h« zu überschreiben, welches auch in Paket libc6-dev-amd64:i386 2.23-0ubuntu9 ist
UpgradeStatus: Upgraded to xenial on 2016-11-07 (263 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.