make monarch build compatible for both conda and uv

[JenniferWang]

Summary:

The Problem

Basically currently the monarch wheel cannot be installed by uv:

ImportError: libpython3.10.so.1.0: cannot open shared object file: No such file or directory

Root Cause

The root cause is

• monarch wheel is built in Conda environment with rpaths baked into the compiled .so files
• uv installs Python in a different location (~/.local/share/uv/python/...), and therefore the baked-in paths don't exist in uv environments

Proper Fix

There are workaround for uv installation, e.g. set LD_LIBRARY_PATH to point to uv's Python library directory, but I think we should do a proper fix to the monarch build since ChatGPT said "Best practice is not to link extensions against libpython on Unix; the loader resolves Python symbols from the running interpreter. PyO3’s extension-module feature exists to avoid linking to libpython altogether. Manylinux guidance and PyO3 docs echo this." https://github.com/pypa/manylinux/issues/69?utm_source=chatgpt.com

This diff is an attempt to use extension-module feature and roughly does two things

• Turn on the feature (in BUCK)
• Remove the hardcoded rpath from setup.py

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Appendix

Workaround by setting LD_LIBRARY_PATH

1. Find your uv Python location:

uv run python -c "import sys; print(sys.executable)"
# Example output: /home/user/.local/share/uv/python/cpython-3.12.12-linux-x86_64-gnu/bin/python3.12

2. Set LD_LIBRARY_PATH:

# For Python 3.12 (adjust version as needed)
export LD_LIBRARY_PATH="$HOME/.local/share/uv/python/cpython-3.12.12-linux-x86_64-gnu/lib:$LD_LIBRARY_PATH"

Differential Revision: D86537232

[meta-codesync]

@JenniferWang has exported this pull request. If you are a Meta employee, you can view the originating Diff in D86537232.