[libcgroup] added new port

[t43rr7]

• Changes comply with the maintainer guide.
• The name of the port matches an existing name for this component on https://repology.org/ if possible, and/or is strongly associated with that component on search engines.
• Optional dependencies are resolved in exactly one way. For example, if the component is built with CMake, all find_package calls are REQUIRED, are satisfied by vcpkg.json's declared dependencies, or disabled with CMAKE_DISABLE_FIND_PACKAGE_Xxx.
• The versioning scheme in vcpkg.json matches what upstream says.
• The license declaration in vcpkg.json matches what upstream says.
• The installed as the "copyright" file matches what upstream says.
• The source code of the component installed comes from an authoritative source.
• The generated "usage text" is accurate. See adding-usage for context.
• The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
• Only one version is in the new port's versions file.
• Only one version is added to each modified port's versions file.

[dg0yt]

Please reduce the indent to 4 spaces.

[dg0yt]

FTR there is a systemd port in vcpkg.

[t43rr7]

It seems to me, that I tried to link systemd from port and encountered some troubles.

But I'll take a look later and give you know about results, thanks.

[t43rr7]

Maybe it's better to include systemd support to this port as a feature?

[dg0yt]

It is okay to have it explicitly turned off if it simplifies initial port acceptance.
Much better than auto-detection!

[dg0yt]

Maybe it's better to include systemd support to this port as a feature?

This is an option. But vcpkg CI will normally build only one configuration.
(What is upstream's default? What is the general expectation?)

[t43rr7]

There are some nuances with systemd. It's an upstream default.

Build with systemd from vcpkg causes some error that I cannot remember now and need to reproduce.

But the build without one breaks an umbrella header. Unfortunately, libcgroup allow to include only this one via include guards in another headers. This error is caused non-installed systemd.h if systemd is disabled.

My attempts to quickly fix this issue in the upstream today were failed because this header (systemd.h) is used from umbrella include (libcgroup.h) by lex/yacc, that has no ifdefs check.

The solutions I see:

1. Try again to use systemd from vcpkg and fix encountered errors (if ones will reproduce)
2. Explicitly disable systemd and place a patch with removing include guard to allow to include other headers explicitly, but not an umbrella header. As the initial solution.

[t43rr7]

@dg0yt I found a commit, that fixes a bug I described above. It's not included to v3.1.0 release.

I think it's better to make this port without systemd support and add it later. For now I'll just include this patch in port as initial solution.

Also I reproduced error with building systemd from vcpkg, it's caused by my local setup: CentOS 7 + clang, and it's enough :) On systemd with:

• Python lower than 3.7
• Old automake, autoconf, libtool
• Old stdc++

It's impossible to build libsystemd given in vcpkg's port.

[dg0yt]

Okay. It is properly turned off.

[dg0yt]

Suggested change

	"license": "LGPL-2.1",
	"license": "LGPL-2.1-only",

Do not just apply my suggestion. Also run vcpkg format-manifest ports/libcgroup/vcpkg.json.
(There is a GH action for this, and it would flag certain issues. But it didn't run yet.)

[MonicaLiu0311]

The header files can be found via .pc file.

[GO-NFT-GO]

Ok