pixi add only works on the project's supported platform

[konstantinjdobler]

Checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pixi, using pixi --version.

Reproducible example

[project]
channels = ["conda-forge"]
platforms = [
"linux-64", 
# "osx-arm64"
]
name = "bug"

[dependencies]
python = "=3.11.*"

Output:

  × the project is not configured for your current platform
   ╭─[pixi.toml:2:1]
 2 │     channels = ["nvidia", "conda-forge", "pytorch-nightly"]
 3 │ ╭─▶ platforms = ["linux-64",
 4 │ │   #  "osx-arm64"
 5 │ ├─▶ ]
   · ╰──── add 'osx-arm64' here
 6 │     name = "nordwind"
   ╰────
  help: The project needs to be configured to support your platform (osx-arm64).

Issue description

E.g. when on M1 Macs, pixi add ruff would fail when "osx-arm64" is commented out. pixi add --no-install ruff also fails.

Expected behavior

I know pixi supported building lockfiles for another platform some time ago. Is this intended? I am using version 0.11.0.

[ruben-arts]

Using the --no-install to avoid this error is a good idea!

I can't remember that we supported the adding of a package without also being on that platform but that might be something we want to get in there.

[baszalmstra]

I think intially we didnt also install the environment during add. I think we could consider not installing the environment if the platform is not supported. Possibly with a warning? WDYT?

[konstantinjdobler]

Just FYI: it worked for me in 0.6.1 (big jump I know, I just upgraded yesterday).

I think not installing with a warning would be great! The use case of creating lockfiles for another platform might be quite common if the actual code runs on a remote machine with a potentially different OS than the local one.

[tdejager]

I think it would be better to make the --no-install flag function correctly i.e. it should work in this case, because the behavior is explicit when looking ath the CLI and the same regardless of the platform. But I can be convinced otherwise ;)