backends: Use POSIX paths for target paths

[amyspark]

👋

This is a PR that fixes #12191 (at least to the extent that my local project stash could check).

It requires #12144 to fix argument detection.

[DFOVIT]

Feel free to ignore as this is only tangentially related to your problem but i'm pretty sure that this line needs the same Path().as_posix() treatment because meson devenv will generate a vscode env file with paths like c:\folder and you will get surprises when your folder name start with a 'n'. I tested with the Path().as_posix() and it generates a correct vscode env file for windows.

[xclaesse]

I'm a bit worried that scattering millions of Path().as_posix() and replace('\\', '/') in random places of Meson is going to be slow and inconsistent. Most of the time it is to workaround broken tools that should instead get fixed.

Alternatively, we could make a project wide search-and-replace to ban usage of os.path.join() and str(Path()), and ensure all our paths are always posix from the beginning, instead of fixing them in random places.

[amyspark]

Most of the time it is to workaround broken tools that should instead get fixed.

I could agree -- in this case, Microsoft Clang not accepting Windows-style paths.

But, if you check the changes that are necessary in the unit tests, this assertion also applies to Meson itself 😃 so the proper fix would be to use one or the other consistently. But there are 300+ places where this is used, so I don't quite know which ones are for internal consumption only and which ones do are passed externally.

[amyspark]

@eli-schwartz I just found #12564 which solves a lot of the issues I was facing. However, there are a couple spots that still needed fixing when using Microsoft clang. I've rebased and fixed them here, and rephrased the commit to clarify that.

[nirbheek]

Needs rebasing, branch has conflicts.

[nirbheek]

LGTM, since all these are places where we were using os.path.join and now are using as_posix().

For future reference: replacing os.path.join good, and str.replace('\\', '/') BAD BAD BAD.

[jpakkane]

Unfortunately this had to be reverted because it was breaking projects in the wild. :(