Fix custom user dir option.

[gzotti]

Description

In our Google forum https://groups.google.com/g/stellarium/c/js2v-tkERIw/m/RfdXb0MKAwAJ we have an issue reported about what happens if you give --user-dir option on the command line. When dir is relative and does not exist, it fails to create the directory. Some other errors seem to follow then.

This PR should fix that.

Fixes # (issue)

Screenshots (if appropriate):

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] This change requires a documentation update
• [ ] Housekeeping

How Has This Been Tested?

Start Stellarium from the command line, Provide --user-dir ppp. Earlier: fail to create ppp Now: creates ppp and uses it.

Test Configuration:

• Operating system: Win11
• Graphics Card: irrelevant

Checklist:

• [x] My code follows the code style of this project.
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation (header file)
• [ ] I have updated the respective chapter in the Stellarium User Guide
• [x] My changes generate no new warnings (only those intended...)
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules

[github-actions[bot]]

Great PR! Please pay attention to the following items before merging:

Files matching src/**/*.cpp:

• [ ] Are possibly unused includes removed?

This is an automatically generated QA checklist based on modified files.

[github-actions[bot]]

Hello @gzotti!

Please check the fresh version (development snapshot) of Stellarium: https://github.com/Stellarium/stellarium-data/releases/tag/weekly-snapshot

[github-actions[bot]]

Hello @gzotti!

Please check the latest stable version of Stellarium: https://github.com/Stellarium/stellarium/releases/latest