Add Hexl/1.2.4

[syoliver]

Specify library name and version: hexl/1.2.4

Intel Homomorphic Encryption (HE) Acceleration Library
https://github.com/intel/hexl

Optional dependency of palisade, a cryptography library

---

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• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the conan-center hook activated.

[uilianries]

Thank you for your contribution. Please, consider Conan V2 migration for future PRs: https://github.com/conan-io/conan-center-index/blob/master/docs/v2_migration.md

[github-actions]

Hooks produced the following warnings for commit fd618a7

hexl/1.2.4

post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library './lib/libhexl.so' links to system library 'm' but it is not in cpp_info.system_libs.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library './lib/libhexl_debug.so' links to system library 'm' but it is not in cpp_info.system_libs.

[uilianries]

Almost good to go.

[uilianries]

LGTM

[conan-center-bot]

All green in build 12 (98519086b81a499c65cbc1198549476af0c2ddaf):

• hexl/1.2.4@:
  All packages built successfully! (All logs)

  🔸 Informative: This recipe is not ready for Conan v2

  _{We have started the migration process to Conan v2 and exporting recipes successfully will be required in the future.
  This is just an informative note to gain awareness about the process, no need to take any action. The plan is to enforce smaller steps that are easier to fix and, eventually, this conan export step will work.
  See the recipe migration guide to know more about the changes required.}

  ERROR: Error loading conanfile at '/home/conan/w/prod_cci_PR-11994/recipes/hexl/all/conanfile.py': Unable to load conanfile in /home/conan/w/prod_cci_PR-11994/recipes/hexl/all/conanfile.py
    File "<frozen importlib._bootstrap_external>", line 728, in exec_module
    File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
    File "/home/conan/w/prod_cci_PR-11994/recipes/hexl/all/conanfile.py", line 1, in <module>
      from conans import CMake, tools
  ImportError: cannot import name 'CMake' from 'conans' (/opt/pyenv/versions/3.7.13/lib/python3.7/site-packages/conans/__init__.py)