Add PyInstaller-based bundling support for runexec

[saurabh12nxf]

This PR adds the ability to create a standalone bundled version of runexec using PyInstaller, addressing #1243.

Implementation

• Approach: PyInstaller
• Binary Size: 17 MB
• Dependencies: Only standard system libraries (libc, libdl, libz, libpthread)
• Build Time: ~30 seconds

Features

✅ All core runexec features work:

• Command execution
• Resource limits (--memlimit, --timelimit)
• Cgroups support
• Container mode (on native Linux)
• ctypes syscalls work correctly

Files Added

• bundling_investigation/runexec.spec - PyInstaller configuration
• bundling_investigation/build_bundle.sh - Production build script
• bundling_investigation/test_pyinstaller.sh - Testing script
• bundling_investigation/test_nuitka.sh - Alternative approach (reference)
• bundling_investigation/README.md - Investigation results
• doc/bundling.md - User documentation

Testing

Tested on Ubuntu 24.04:

• ✅ Version check
• ✅ Command execution
• ✅ Resource limits
• ✅ Cgroups
• ✅ Container mode (except WSL overlay limitation)

Usage

cd bundling_investigation
./build_bundle.sh
./dist/runexec --version

Known Limitations

• Container mode may not work in WSL2 due to overlay filesystem limitations (use --no-container flag)
• Binary is architecture-specific (x86_64)

Fixes #1243