Add build2 package support

[Klaim]

WARNING: Please do not merge yet! See below.

We are currently in the process of packaging spdlog for build2, we have it working (even on unsupported Windows, see for example: https://ci.stage.build2.org/@a993b64e-8ba2-422e-97d7-250cdb5828e0?builds=&pv=&tc=*&cf=&mn=&tg=&rs=*)

This change simply adds the necessary information to use this package when using build2. Some notes:

• not sure how to give the info succintly because build2 allows packages to come from different sources, including the git repository of the package - in doubt I just linked to the future community repository address providing all the info, but the other package manager didn't do it like that so not sure if it's ok for you?;
• build2 distinguish the package (depends: spdlog <some-version-scheme>, added in the manifest file of a build2 project) and the target (spdlog%lib{spdlog} imported in a buildfile) because packages can contain several targets. I was not sure how to formulate that here, so feel free to tell me if I should just provide the name of the package and not more info?

The package isn't available yet so this have to be merged only once it is made available (probably in a few days).

[gabime]

what is build2? never heard of it

[Klaim]

It's a build-system combined with a package manager, see https://build2.org
A bit like if you used conan+make or conan+cmake/make or etc. but more "coherent".

It's known to be one of the first buildsystem handling C++ modules (when preview implementations were made available), among other things.

Once the package will be published, it will be available on https://cppget.org which is the OSS community central repository. But build2 also allows to use build2 packages/projects inside git repositories, so that's another option (when you want to use a tweaked version of the package for example).

[Klaim]

The build2 package for spdlog v1.8.2 is currently in the publication queue: https://queue.cppget.org/spdlog/1.8.2+1
There you can also see the build output (only the tests are executed for testing).
There are a few warnings on Windows (which I understand is not officially supported, but it actually works as long as you link with the right system library) and we deactivated gcc/mingw on Windows because some tests fails (but build works).

Waiting for the publication to be done.

[gabime]

There are a few warnings on Windows (which I understand is not officially supported, but it actually works as long as you link with the right system library)

What do you mean ? Windows is officially supported

[Klaim]

There are a few warnings on Windows (which I understand is not officially supported, but it actually works as long as you link with the right system library)

What do you mean ? Windows is officially supported

Sorry, I meant spdlog as shared library on Windows.
Or maybe this comment is not up to date?

[Klaim]

spdlog package v1.8.2 is now online: https://cppget.org/spdlog

You can merge this now if you want, or point me tweaks you would like me to do.

[gabime]

Or maybe this comment is not up to date?

It is not updated. Shared build is supported.

[gabime]

@Klaim Something doesn't look right in the command example, so I reverted.
What is the exact command to use?

[Klaim]

@gabime There is no specific "command": you just add the package as dependency in your build2 project's manifest file like this depends: spdlog ^1.8.2 (for any version compatible with 1.8.2 for example) and the buildsystem will invoke the package manager automatically at the next command to retrieve and initialize that package, or will do so when you initialize the project in a new configuration (so you have as many libraries built as configurations - note that build2 only have source packages).

After that you can then import the spdlog%lib{spdlog} target to make your own targets depends on it (in buildfiles where your targets are defined).
This is assuming your project relies on cppget.org to get it's packages, which is can be done manually or by adding it in another project's file. Most build2 projects rely on that repository.

It's similar to conan in the sense that there is a file in your project listing the packages that project depends on, and then the targets in it are made available to your build scripts (CMake scripts for example).

So here I just named the package and the target to import, similarly to the conan line. I'm assuming the user knows build2 so they can easilly use that information, as for the other package managers. I tried to be short because the other ones are short, and the conan one just name the package and probably assume the user knows what to do with it.

Or do I misunderstand what you want in there?

[gabime]

so, maybe something like

build2: depends: spdlog ^1.8.2 ?

[Klaim]

Works for me.
It might be obscure for newcomers (where do they write add?) but it's obvious to people used to build2

[gabime]

btw I am a big fan of cargo, so I really hope build2 succeeds!

[Klaim]

Nice :D

I updated the branch, should I make another PR?

[gabime]

No need. I already updated

[Klaim]

Thanks!