Fix #124454: Allow BF_DIST_BIN to be a symlink

In `blender-launcher` on linux, the `$0` could be assigned to
a symlink instead of an actual directory, which may cause infinite
chaining of the command which ultimately gives an arguent string that's
way too long. This fix prevents that by using `readlink -f` first.

This fix was implemented by @Joel-Schumacher

Ref: !124533

release/bin/blender-launcher

@@ -1,5 +1,5 @@
 #!/bin/sh
-BF_DIST_BIN=$(dirname "$0")
+BF_DIST_BIN=$(dirname $(readlink -f "$0"))
 BF_PROGRAM="blender"
 
 # Add own lib folder first, because Steam or other environments may set an