Set SingleMainWindow to true for Linux

[mrclary]

Enforces single instance on Linux.

Checklist

• Used a personal fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• Reset the build number to 0 (if the version changed)
• Re-rendered with the latest conda-smithy (Use the phrase @conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• Ensured the license file is being packaged.

This feature is now incorporated into menuinst=2.2.0 (conda/menuinst#265).
I'm not certain yet whether including it here will raise an error for menuinst=2.1.2 or just be ineffective.

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe/meta.yaml) and found it was in an excellent condition.

I do have some suggestions for making it better though...

For recipe/meta.yaml:

• ℹ️ noarch: python recipes should usually follow the syntax in our documentation for specifying the Python version.
  • For the host section of the recipe, you should usually use python {{ python_min }} for the python entry.
  • For the run section of the recipe, you should usually use python >={{ python_min }} for the python entry.
  • For the test.requires section of the recipe, you should usually use python {{ python_min }} for the python entry.
  • If the package requires a newer Python version than the currently supported minimum version on conda-forge, you can override the python_min variable by adding a Jinja2 set statement at the top of your recipe (or using an equivalent context variable for v1 recipes).

[mrclary]

@conda-forge-admin, please rerender

[mrclary]

@ccordoba12, I've checked this artifact on my Ubuntu VM and found that the additional tag in the json file is gracefully ignored by menuinst 2.1.2, so we can safely merge this. The feature will only be recognized after updating to menuinst >=2.2.0.

[ccordoba12]

Looks good to me, thanks @mrclary!