linkage_checker: add libquadmath

[danielnachun]

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We have noticed in Homebrew/homebrew-core#123264 that libquadmath.so.0 is also provided by GCC. This is primarily used by Fortran applications (in which case libquadmath.so.0 is provided by brewed GCC), but on occasion C or C++ programs link to this as well and brew audit should allow linkage to the system version of this library.

[BrewTestBot]

Review period will end on 2023-02-17 at 03:22:02 UTC.

[Bo98]

Is it commonly installed by default by the system though? We keep our system dependencies minimal to what are provided by default in virtually all distributions (glibc, libstdc++, libgcc_s, etc.).

If the system version of library wasn't found, it's not like brew will auto install GCC - it will try to build from source instead, which isn't an optimal experience.

[iMichka]

It's preinstalled (on docker at least, with ubuntu 22). I think it's just part of the standard gcc installation (under /usr/lib/gcc/x86_64-linux-gnu/11/libquadmath.so).
We ask our users to have gcc installed on Linux as part of the build essentials or development tools.

Change looks good to me.

[Bo98]

We ask our users to have gcc installed on Linux as part of the build essentials or development tools.

We might suggest it in places but we do not require the full GCC toolchain to be installed anymore.

It's not been required for a while, but it was only cleaned up from documentation last year: 1882ae4

At the moment however, we do check /usr/bin/gcc but that really ought to be rewritten to check libstdc++.so instead as the current logic is incorrect on Debian 11. So we do perhaps have an accidental requirement on the dev toolchain due to that bug, and can get away with allowing libquadmath as a result.

[Bo98]

For some reason I actually misread this PR as libgfortran at first, which definitely isn't always installed as standard but is a part of the full GCC toolchain we provide.

libquadmath however we can probably get away with so I'm fine either way.

[carlocab]

algol68g will need a Linux bottle dispatched when this is merged.

[cho-m]

On Debian/Ubuntu, libquadmath0 is pulled in via https://packages.debian.org/sid/libgcc-11-dev

What is required minimal packages to install on Fedora? I don't think the 64-bit library (libquadmath) is automatically pulled in with gcc.

For example, Fedora's algol68g package has a direct dependency on libquadmath - https://packages.fedoraproject.org/pkgs/algol68g/algol68g/fedora-rawhide.html#dependencies

[MikeMcQuaid]

Disabling auto-merge for now so this is in 4.0.2 not 4.0.1.

[iMichka]

On Fedora/centos we ask for the 'Development tools' package.
https://docs.brew.sh/Homebrew-on-Linux#requirements

This brings in gcc. But we will to ask our users to install gcc-gfortran for that platform.

Should algol68g not depend on gcc instead?

[BrewTestBot]

Review period ended.