cli11: Compile by default, add header_only option

[vasama]

Summary

CLI11 supports static library builds. This PR changes the recipe to build a static library by default and adds a header only option.

Motivation

Fixes #25737.

Details

---

• Read the contributing guidelines
• Checked that this PR is not a duplicate: list of PRs by recipe
• Tested locally with at least one configuration using a recent version of Conan

[CLAassistant]

All committers have signed the CLA.

[uilianries]

LGTM

[conan-center-bot]

Conan v1 pipeline ❌

Warning

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Failure in build 7 (23540de0dad5d529339be04e6eaaa5548f521676):

• cli11/2.4.2:
  Didn't run or was cancelled before finishing

• cli11/2.4.1:
  Didn't run or was cancelled before finishing

• cli11/2.3.1:
  Didn't run or was cancelled before finishing

• cli11/2.4.0:
  Didn't run or was cancelled before finishing

• cli11/2.2.0:
  Didn't run or was cancelled before finishing

• cli11/2.0.0:
  Didn't run or was cancelled before finishing

• cli11/1.9.1:
  Didn't run or was cancelled before finishing

• cli11/2.1.2:
  Didn't run or was cancelled before finishing

• cli11/2.1.1:
  Error running command conan info cli11/2.1.1@#544cfa0b8f8fd581ab5314a442267cb3 --json {jsonName} --dry-build -pr {profileName}:

  [settings]
  arch=x86_64
  build_type=Release
  compiler=gcc
  compiler.libcxx=libstdc++11
  compiler.version=5
  os=Linux
  [options]
  cli11:header_only=False
  
  ...
  ERROR: cli11/2.1.1: option 'header_only' doesn't exist
  Possible options are []
  

• cli11/2.3.0:
  Didn't run or was cancelled before finishing

• cli11/2.3.2:
  Didn't run or was cancelled before finishing

---

^{Note: To save resources, CI tries to finish as soon as an error is found. For this reason you might find that not all the references have been launched or not all the configurations for a given reference. Also, take into account that we cannot guarantee the order of execution as it depends on CI workload and workers availability.}

[uilianries]

Suggested change

	"header_only": False
	"header_only": True

Keep header-only as True, so the Package ID will be the same as for previous versions.

[vasama]

That really sucks because header only builds are very undesirable. It ends up breaking unrelated code due to leaked implementation details like included system headers. That's what prompted me to create the issue and PR in the first place.

[AbrilRBS]

The main issue here is that upstream also defaults to a single-header installation, and the compilation behaviour is opt-in, so with this we would be following the choices on upstream

[vasama]

It's a very user hostile default though, only motivated by ease of distribution, which is hardly a concern if one is using Conan.

[uilianries]

@vasama You still can build using the option that you need in your configuration as well. In CCI we mostly follow upstream default behavior, as it will affect all users and will reflect the upstream build as well.

[vasama]

I'm aware of that. I just want to make it clear that header only is a bad and pointless default.