fix: work around pip bug

[henryiii]

Fix:

• [BUG] Cannot find the cmake module in a wheel build venv when the cmake executable is installed in another venv #586
• installed cmake "binary" fails to run when used used as a pip install dependency #324.

[henryiii]

Writing a script doesn't work on Windows. You have to create a shim there, pip doesn't seem to do it for you if you give it a Python script. So there are a few options:

• Use dynamic-metadata to create script entrypoints on Windows, and Unix only gets the fix. Still might be a bit broken on Windows.
• Write a shim (we have a compiler, after all)
• Take a stab at moving the executable to the Scripts directory. This is the nicest solution, but I've avoided it since it needs to know where the modules files are. If I can put them into the bin folder in a subfolder, that's likely the most reliable, but I might also be able to refer up a certain number of directories then back down. Or write a shim.

[mayeut]

since popping the PYTHONPATH environment variable seemed to work, I tried to modify the shebang to use -E and in order to simplify the script a bit (not sure it would be safer yet, just trying it out). uv does not respect arguments to the shebang and creates broken scripts (astral-sh/uv#14470).