[boost-predef] Add Modular Boost Predef recipe

[fpelliccioni]

boost-predef/1.83

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This PR introduces the first modular recipe for the Boost Libraries in the Conan Center Index, starting with Boost Predef. Boost Predef is a header-only library with no dependencies on other packages. The addition of this recipe paves the way for future modular recipes for each Boost library. The Boost Predef recipe is designed to serve as a template for these subsequent additions, promoting a more organized and modular approach to managing Boost Libraries in Conan.

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• I've read the contributing guidelines.
• I've used a recent Conan client version close to the currently deployed.
• I've tried at least one configuration locally with the conan-center hook activated.

[conan-center-bot]

Conan v1 pipeline ❌

Failure in build 5 (8b01f2b323c2666573b5903b3935a9eb65884045):

• boost-predef/1.83.0:
  Error running command conan export recipes/boost-predef/all/conanfile.py boost-predef/1.83.0@:

  [HOOK - conan-center.py] pre_export(): [DEPRECATED GLOBAL CPPSTD (KB-H001)] OK
  [HOOK - conan-center.py] pre_export(): [REFERENCE LOWERCASE (KB-H002)] OK
  [HOOK - conan-center.py] pre_export(): [RECIPE METADATA (KB-H003)] OK
  [HOOK - conan-center.py] pre_export(): [HEADER_ONLY, NO COPY SOURCE (KB-H005)] OK
  [HOOK - conan-center.py] pre_export(): [FPIC OPTION (KB-H006)] OK
  [HOOK - conan-center.py] pre_export(): [VERSION RANGES (KB-H008)] OK
  [HOOK - conan-center.py] pre_export(): [RECIPE FOLDER SIZE (KB-H009)] Total recipe size: 7.142578125 KB
  [HOOK - conan-center.py] pre_export(): [RECIPE FOLDER SIZE (KB-H009)] OK
  [HOOK - conan-center.py] pre_export(): [EXPORT LICENSE (KB-H023)] exports: None
  [HOOK - conan-center.py] pre_export(): [EXPORT LICENSE (KB-H023)] exports: None
  [HOOK - conan-center.py] pre_export(): [EXPORT LICENSE (KB-H023)] OK
  [HOOK - conan-center.py] pre_export(): [TEST PACKAGE FOLDER (KB-H024)] OK
  [HOOK - conan-center.py] pre_export(): [META LINES (KB-H025)] OK
  [HOOK - conan-center.py] pre_export(): [CMAKE MINIMUM VERSION (KB-H028)] OK
  [HOOK - conan-center.py] pre_export(): [TEST PACKAGE - RUN ENVIRONMENT (KB-H029)] OK
  [HOOK - conan-center.py] pre_export(): [SYSTEM REQUIREMENTS (KB-H032)] OK
  [HOOK - conan-center.py] pre_export(): [CONANDATA.YML FORMAT (KB-H030)] OK
  [HOOK - conan-center.py] pre_export(): [TEST PACKAGE - NO IMPORTS() (KB-H034)] OK
  [HOOK - conan-center.py] pre_export(): [NO AUTHOR (KB-H037)] OK
  [HOOK - conan-center.py] pre_export(): [NOT ALLOWED ATTRIBUTES (KB-H039)] OK
  [HOOK - conan-center.py] pre_export(): [NO TARGET NAME (KB-H040)] OK
  [HOOK - conan-center.py] pre_export(): [NO FINAL ENDLINE (KB-H041)] OK
  [HOOK - conan-center.py] pre_export(): [NO REQUIRES.ADD() (KB-H044)] OK
  [HOOK - conan-center.py] pre_export(): [DELETE OPTIONS (KB-H045)] OK
  [HOOK - conan-center.py] pre_export(): [CMAKE VERBOSE MAKEFILE (KB-H046)] OK
  [HOOK - conan-center.py] pre_export(): [CMAKE VERSION REQUIRED (KB-H048)] OK
  [HOOK - conan-center.py] pre_export(): [CMAKE WINDOWS EXPORT ALL SYMBOLS (KB-H049)] OK
  [HOOK - conan-center.py] pre_export(): [DEFAULT OPTIONS AS DICTIONARY (KB-H051)] OK
  [HOOK - conan-center.py] pre_export(): [CONFIG.YML HAS NEW VERSION (KB-H052)] OK
  [HOOK - conan-center.py] pre_export(): [PRIVATE IMPORTS (KB-H053)] OK
  [HOOK - conan-center.py] pre_export(): [SINGLE REQUIRES (KB-H055)] OK
  [HOOK - conan-center.py] pre_export(): [TOOLS RENAME (KB-H057)] OK
  [HOOK - conan-center.py] pre_export(): [ILLEGAL CHARACTERS (KB-H058)] OK
  [HOOK - conan-center.py] pre_export(): [CLASS NAME (KB-H059)] OK
  [HOOK - conan-center.py] pre_export(): [NO CRLF (KB-H060)] OK
  [HOOK - conan-center.py] pre_export(): [NO BUILD SYSTEM FUNCTIONS (KB-H061)] OK
  [HOOK - conan-center.py] pre_export(): [TOOLS CROSS BUILDING (KB-H062)] OK
  [HOOK - conan-center.py] pre_export(): [INVALID TOPICS (KB-H064)] OK
  [HOOK - conan-center.py] pre_export(): [NO REQUIRED_CONAN_VERSION (KB-H065)] OK
  [HOOK - conan-center.py] pre_export(): [TEST_TYPE MANAGEMENT (KB-H068)] OK
  [HOOK - conan-center.py] pre_export(): [TEST PACKAGE - NO DEFAULT OPTIONS (KB-H069)] OK
  [HOOK - conan-center.py] pre_export(): [MANDATORY SETTINGS (KB-H070)] OK
  [HOOK - conan-center.py] pre_export(): [PYLINT EXECUTION (KB-H072)] OK
  [HOOK - conan-center.py] pre_export(): [REQUIREMENT OVERRIDE PARAMETER (KB-H075)] OK
  [HOOK - conan-center.py] pre_export(): ERROR: [CONAN CENTER INDEX URL (KB-H027)] The attribute 'url' should point to: https://github.com/conan-io/conan-center-index (https://github.com/conan-io/conan-center-index/blob/master/docs/error_knowledge_base.md#KB-H027-CONAN-CENTER-INDEX-URL) 
  ERROR: [HOOK - conan-center.py] pre_export(): Some checks failed running the hook, check the output
  

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[fpelliccioni]

@prince-chrismc @RubenRBS guys could you please help me determining what's wrong in V1 ?
I am not able to see the full error log.

[uilianries]

@fpelliccioni Thank you for your intention of boost modularization, but it's not supported for now: https://github.com/conan-io/conan-center-index/blob/master/docs/faqs.md#can-we-add-package-which-are-parts-of-bigger-projects-like-boost

Indeed is a wish having it available, but there are other points to be solved first. We still have a limitation with b2 when building everything modular, for instance.

There was an initial effort on the repo https://github.com/conan-io/modular-boost. But need to re-visit.