commit dd9584b352169f8050bd3b64caf3470b81ffafc9
author Mathieu Malaterre <mathieu.malaterre@gmail.com> Fri Nov 19 11:02:21 2021 +0100
committer Brad King <brad.king@kitware.com> Fri Nov 19 09:40:06 2021 -0500
tree 41cbb5b4c274732d19011a25d0664c7b3c06c903
parent 7d1cb6496e5fbe5ed9668e95141ade3514b52c93

GNUInstallDirs: Apply Debian multiarch LIBDIR to more prefixes

On typical Debian amd64 system (bullseye), multiarch is setup as:

```
% cat /etc/ld.so.conf.d/x86_64-linux-gnu.conf
/usr/local/lib/x86_64-linux-gnu
/lib/x86_64-linux-gnu
/usr/lib/x86_64-linux-gnu
```

Where:

```
% apt-cache policy libc6:amd64
libc6:
  Installed: 2.31-13+deb11u2
  Candidate: 2.31-13+deb11u2
  Version table:
 *** 2.31-13+deb11u2 500
        500 http://deb.debian.org/debian bullseye/main amd64 Packages
        100 /var/lib/dpkg/status
```

Update GNUInstallDirs to support all three cases `/`, `/usr/` and
`/usr/local/`.

Fixes: #19698