Fresh installation in conda environment does not find `libpython`, missing RPATH

[maxnoe]

The RUNPATH is not set appropriately:

$ mamba create -n proposal python=3.12
$ conda activate proposal
$ pip install -v --no-cache proposal 2>&1 | tee build-log.txt
$ python -c 'import proposal'
❯ python -c 'import proposal'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: libpython3.12.so.1.0: cannot open shared object file: No such file or directory
❯ ldd ~/.local/conda/envs/proposal/lib/python3.12/site-packages/proposal.cpython-312-x86_64-linux-gnu.so
	linux-vdso.so.1 (0x00007f205e07a000)
	libpython3.12.so.1.0 => not found
	libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f205d400000)
	libm.so.6 => /lib64/libm.so.6 (0x00007f205df63000)
	libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f205df37000)
	libc.so.6 => /lib64/libc.so.6 (0x00007f205d20e000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f205e07c000)
❯ readelf -a ~/.local/conda/envs/proposal/lib/python3.12/site-packages/proposal.cpython-312-x86_64-linux-gnu.so | grep RUNPATH
 0x000000000000001d (RUNPATH)            Library runpath: [$ORIGIN]

A working extension I have has this r(un)path:

❯ readelf -a ~/.local/conda/envs/protozfits-dev/lib/python3.12/site-packages/protozfits/rawzfits.cpython-312-x86_64-linux-gnu.so | grep RPA
 0x000000000000000f (RPATH)              Library rpath: [/home/maxnoe/.local/conda/envs/protozfits-dev/lib:$ORIGIN:$ORIGIN/../lib64]

(I.e. the conda envs "lib" directory is in there).

[maxnoe]

I cannot get over the fact that an issue about something not being found got issue number 404.