Defines the directory of the GBC component for Universal Rendering.

The FGLGBCDIR environment variable can be used to define the directory where the GBC component must be loaded from.

The GBC component will be searched in the following directories:
  1. The appdir/gbc directory, where appdir is the directory where the program file is located,
  2. The directory defined in the FGLGBCDIR environment variable,
  3. The $FGLDIR/web_utilities/gbc/gbc directory.
If defined, make sure that FGLGBCDIR is set to a directory containing the GBC component files.
Note: The FGLGBCDIR environment variable is provided to select a given GBC in a development context when using the GUI direct mode. Do not use FGLGBCDIR in a production context: If a specific GBC is needed in production, consider shipping it in appdir/gbc. Otherwise, use the GBC available by default.