intro-install-plan.json does not match with intro-installed.json

[lithomas1]

Describe the bug

The files listed in the intro-install-plan.json do not match with the files installed (listed in intro-installed.json).
This causes problems for meson-python, which uses intro-install-plan.json to find installed files.

In particular, on Windows, when building in release mode, pdb files will be listed in the install-plan but not installed, with a message like

File 'pandas\\_libs\\window\\indexers.cp38-win_amd64.pdb' not found, skipping

In addition, folders installed with install_subdir are not listed in the install-plan.

To Reproduce
Please include your meson.build files, preferably as a minimal toy example showing the issue.
You may need to create simple source code files (don't include private/proprietary code).

I found this problem while trying to port pandas to meson. Here is the code to reproduce.

git clone https://github.com/lithomas1/pandas.git@meson-poc
cd pandas
python -m build

It should be reproducible without pandas, though. I'll try to make a MRE when I have some time.
Expected behavior
A clear and concise description of what you expected to happen.

files listed in intro-install-plan should match files in intro-installed.

system parameters

• Is this a cross build or just a plain native build (for the same computer)?
  native
• what operating system (e.g. MacOS Catalina, Windows 10, CentOS 8.0, Ubuntu 18.04, etc.)
  Windows
• what Python version are you using e.g.
  3.8.0
• what meson --version
  0.63.0
• what ninja --version if it's a Ninja build

[eli-schwartz]

@FFY00, you originally implemented #9130 for your PEP 517 backend, what's the story here?

[FFY00]

I think the issue is that we don't install pdb files in release mode, but install-plan doesn't take that into account and still lists it.

[lithomas1]

The issue with missing install subdirs can probably be fixed just by adding 'subdirs': installdata.subdirs here.

meson/mesonbuild/mintro.py

Lines 136 to 140 in f8ebfdf

	for key, data_list in {
	'data': installdata.data,
	'man': installdata.man,
	'headers': installdata.headers,
	}.items():

I'm still not sure about the pdb files, though. The band-aid fix would be to just skip targets that don't exist on the file-system, but there seems to be a bigger issue here. @eli-schwartz Do you happen to know why the pdb files seem to be listed as install targets even in release mode?