Add pynacl

[Copilot]

This PR adds the PyNaCl package recipe to emscripten-forge. PyNaCl is a Python binding to the Networking and Cryptography (NaCl) library, providing high-level cryptographic primitives for Python applications.

Changes Made

• Recipe Definition: Created recipes/recipes_emscripten/pynacl/recipe.yaml with:

  • PyNaCl version 1.6.0 (latest stable release)
  • Proper build dependencies including cffi (>=1.4.1) and make for compiling bundled libsodium
  • Standard emscripten-forge Python package build configuration
  • Correct source URL and SHA256 hash from PyPI
  • Added license_file field pointing to LICENSE file

• Cross-compilation Support: Added recipes/recipes_emscripten/pynacl/build.sh script to handle cross-compilation:

  • Sets CHOST="wasm32-unknown-emscripten" for autotools recognition
  • Configures LIBSODIUM_CONFIGURE_ARGS="--host=wasm32-unknown-emscripten" for PyNaCl's bundled libsodium
  • Ensures proper cross-compilation setup for the emscripten-wasm32 target platform

• Testing: Added recipes/recipes_emscripten/pynacl/test_import_pynacl.py with comprehensive import tests covering:

  • Core nacl module
  • Key submodules: secret, public, utils, hash, signing, encoding

Technical Details

PyNaCl bundles its own copy of libsodium which gets compiled during the build process, requiring make as a build dependency and special cross-compilation configuration. The recipe follows established patterns from other cryptographic packages in the repository (like cryptography and cffi).

The build script addresses the autotools configure error by properly setting environment variables that PyNaCl's bundled libsodium recognizes, ensuring the configure script knows it's being cross-compiled for WebAssembly.

The package provides Python bindings for:

• Symmetric encryption (nacl.secret)
• Public-key cryptography (nacl.public)
• Digital signatures (nacl.signing)
• Cryptographic hashing (nacl.hash)
• Encoding utilities (nacl.encoding)

Fixes #2873.

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[IsabelParedes]

@copilot implement changes

[IsabelParedes]

@copilot add --host

configure: error: cannot run C compiled programs.
      If you meant to cross compile, use '--host'.

[Copilot]

@copilot add --host

...

Added --host=wasm32-unknown-emscripten flag via build.sh script to fix cross-compilation error. The script sets environment variables that will be passed to the bundled libsodium configure script. Commit 184cb29