I've addressed this in my code, but it's a little awkward and somewhat brittle because the code cannot know what makes for a valid luatex-cache directory:

    private boolean reinitialize() {

      // variable assignments ... exists = check for luatex-cache directory

      mArgs.clear();
      mArgs.add( TYPESETTER.getName() );

      if( exists ) {
        mArgs.add( "--autogenerate" );
        mArgs.add( "--script" );
        mArgs.add( "mtx-context" );
        mArgs.add( ... remaining args ... );
      }
      else {
        mArgs.add( "--generate" );
      }

      return exists;
    }

    private boolean typeset() throws Exception {
      return reinitialize() ? call() : call() && reinitialize() && call();
    }

    // Invoke ConTeXt to either typeset the document or generate the cache directory

    public Boolean call() throws Exception {
      final var builder = new ProcessBuilder( mArgs );
      builder.directory( mDirectory.toFile() );

      final var cacheDir = getCacheDir();
      final var env = builder.environment();
      env.put( "TEXMFCACHE", cacheDir.toString() );

      builder.redirectOutput( DISCARD );
      builder.redirectError( DISCARD );

      final var process = builder.start();
      process.waitFor();
      final var exit = process.exitValue();
      process.destroy();
      return exit == 0;
    }

Also, unless my application installs ConTeXt, setting the TEXMFCACHE directory before the installation begins will require asking users to do this. Ideally, using the software would take the following steps:

1. Download text editor

2. Download and install ConTeXt (e.g., click link, extract archive, run install.sh)

3. Run text editor

4. Export PDF (editor configures ConTeXt as required, reducing the number of steps for end users)

At some point in the future, the editor may prompt the user for permission to install ConTeXt on their behalf---to simplify step 2---but that's much more effort.

Stay safe!