[python-wrapper] Re-populate REPLIT_LD_LIBRARY_PATH

[blast-hardcheese]

Why

During the last refactor we lost the default fallback Python runtime, removing critical C++ libraries from the path. This was because the testing environment provided a default value, which did not adequately exercise the default case.

What changed

Mirror the setup between legacy and modern environment builders for clarity.

Test plan

This time, I tested by unsetting the value first...

$ unset REPLIT_LD_LIBRARY_PATH; python main.py

then running the following (main.py):

import os

[var] = [x for x in open('/proc/self/environ').read().split('\0') if x.startswith('REPLIT_LD_LIBRARY_PATH=')]

for dir in var.split("=", 1)[1].split(':'):
    fpath = os.path.join(dir, 'libstdc++.so.6')
    if os.path.exists(fpath):
        break

print(f"Found {fpath}")
print(os.stat(fpath))

This replicates the lookup logic in ld-audit and verifies that we can find the library we need.

Rollout

Describe any procedures or requirements needed to roll this out safely (or check the box below)

• This is fully backward and forward compatible