Make config file configurable

[capital-G]

from IDE source code - the reason why I don't have all Quarks available in the kernel.

Probably best to make this configurable by using an environment variable.
A slicker version would be to select from multiple sclang kernels, but I don't know if this is possible.

    QString configFile = settings->value("configFile").toString();

[capital-G]

I could not get this to run via the -l flag of

❯ ./sclang -h
Usage:
   sclang [options] [file..] [-]

Options:
   -v                             Print supercollider version and exit
   -d <path>                      Set runtime directory
   -D                             Enter daemon mode (no input)
   -g <memory-growth>[km]         Set heap growth (default 256k)
   -h                             Display this message and exit
   -l <path>                      Set library configuration file
   -m <memory-space>[km]          Set initial heap size (default 2m)
   -r                             Call Main.run on startup
   -s                             Call Main.stop on shutdown
   -u <network-port-number>       Set UDP listening port (default 57120)
   -i <ide-name>                  Specify IDE name (for enabling IDE-specific class code, default "none")
   -a                             Standalone mode (exclude SCClassLibrary and user and system Extensions folders from search path)