Add support out-of-tree builds.
This commit adds a support for out-of-tree builds, i.e, object files,
executables and so on are writen to `$(OUTDIR)` (which defaults to
`build/<BUILD_TARGET>` directory.
This allows building Smalltalk/X from single source tree for multiple
targets.
"*
* Encoding: iso8859-1
*
* $Header: /cvs/stx/stx/projects/smalltalk/d_xfree.rc,v 1.8 2004/11/10 12:06:31 stefan Exp $
*
* MIMEType: application/x-smalltalk-source
*
* ST/X startup configuration file:
* display configuration - XDeep32 (a free XServer for Windows)
*"
!
View defaultStyle:#mswindowsXP.
Screen current supportsDeepIcons:true.