Fix bad use of "ln -sf"

[fizbin]

Description

Changes an ln -sf into separate rm -f and ln -s commands, because ln -sf doesn't do what's expected if the destination is already a link to a directory.

Fixes #985 (Incorrect ln -sf in startup script means that ARM can't restart if ~arm/Music is on a CIFS/Samba share)

Type of change

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• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

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Changed arm_user_files_setup.sh as in this PR, and ARM then restarted smoothly. Without this change, and with a docker -v option that maps /home/arm/Music to a samba share, restarting ARM after running it and shutting it down won't work. (see bug description)

Please also list any relevant details for your test configuration

• Docker
• Other (Please state here)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• [N/A] I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have tested that my fix is effective or that my feature works

Changelog:

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• Change 1: split ln -sf into rm -f and ln -s

Logs

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[sonarcloud]

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[DArtagan]

Wait a second, I think this fix makes two assumptions:

1. That you're using a folder named with capital Music, but the scripts/docker/start_arm_container.sh uses lowercase music. In the original issue, it appears the poster is using a custom start_arm_container.sh script?
2. That you have a symlink where lowercase /home/arm/music is.

The result of these assumptions is that if you are using the default script from this repo, and placing your folders as the docs instruct, then this line will attempt to delete your music folder and replace it with a symlink to a folder that doesn't exist. I say this, because it just happened to me with a fresh setup.

rm: cannot remove '/home/arm/music': Is a directory 

[DArtagan]

Correction / addendum / now I'm even more confused:

While the default scripts/docker/start_arm_container.sh does use a lowercase music, the default arm_user_files_setup.sh uses uppercase Music during its mkdir/chown phase.

It looks like a capitalization change was made to start_arm_container.sh ~7 months ago in #874.