public final ResourceFile getExtensionArchiveDir() {
		return extensionArchiveDir;
	}
Returns the directory where archived application Extensions are stored.  This directory may
contain both zip files and subdirectories.   This directory is only used inside of an
installation; development mode does not use this directory.   This directory is used to ship 
pre-built Ghidra extensions as part of a distribution.
<P>
This should be at the following location:<br>
<ul>
<li><code>{install dir}/Extensions/Ghidra</code></li>
</ul>

@return the application Extensions archive directory.  Could be null if the
  {@link ApplicationLayout} does not support application Extensions.
Ghidra/Framework/Utility/src/main/java/utility/application/ApplicationLayout.java