libpython not loaded under Anaconda

Bug Description

While correctly detected, libpython*.dylib is not found at runtime under miniconda.

Steps to Reproduce

See the complete minimal code.

Backtrace

--- stdout
  cargo:rerun-if-env-changed=PYO3_CROSS
  cargo:rerun-if-env-changed=PYO3_CROSS_LIB_DIR
  cargo:rerun-if-env-changed=PYO3_CROSS_PYTHON_VERSION
  cargo:rerun-if-env-changed=PYO3_CROSS_PYTHON_IMPLEMENTATION
  cargo:rerun-if-env-changed=PYO3_PRINT_CONFIG

  -- PYO3_PRINT_CONFIG=1 is set, printing configuration and halting compile --
  implementation=CPython
  version=3.12
  shared=true
  abi3=false
  lib_name=python3.12
  lib_dir=/Users/runner/miniconda3/lib
  executable=/Users/runner/miniconda3/bin/python
  pointer_width=64
  build_flags=
  suppress_build_script_link_lines=false

  note: unset the PYO3_PRINT_CONFIG environment variable and retry to compile with the above config
...
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 3.78s
     Running `target/debug/pyo3-test`
dyld[6132]: Library not loaded: @rpath/libpython3.12.dylib
  Referenced from: <D47A24F9-530D-36D3-A2DF-66D920E7E1B9> /Users/runner/work/pyo3-test/pyo3-test/target/debug/pyo3-test
  Reason: tried: '/Users/runner/work/pyo3-test/pyo3-test/target/debug/deps/libpython3.12.dylib' (no such file), '/Users/runner/work/pyo3-test/pyo3-test/target/debug/libpython3.12.dylib' (no such file), '/Users/runner/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/aarch64-apple-darwin/lib/libpython3.12.dylib' (no such file), '/Users/runner/.rustup/toolchains/stable-aarch64-apple-darwin/lib/libpython3.12.dylib' (no such file), '/Users/runner/lib/libpython3.12.dylib' (no such file), '/usr/local/lib/libpython3.12.dylib' (no such file), '/usr/lib/libpython3.12.dylib' (no such file, not in dyld cache)
/Users/runner/work/_temp/23791571-1fd0-4d1a-b32c-b63b783c7030.sh: line 5:  6132 Abort trap: 6           cargo run
Error: Process completed with exit code 134.

Your operating system and version

MacOS (Github runner) — also on Linux

Your Python version (python --version)

Python 3.12

Your Rust version (rustc --version)

rustc 1.78.0 (9b00956e5 2024-04-29)

Your PyO3 version

0.21.2

How did you install python? Did you use a virtualenv?

Anaconda

Additional Info

No response

Start with the linked minimal pyo3-test reproduction and its cargo run output; inspect how PyO3 uses the reported lib_dir and how the macOS and Linux runtime loaders search for libpython*.dylib. Done means the Anaconda Python 3.12 library loads at runtime in the reproduction on the affected platforms without a manual workaround.