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
*
* $Header$
*
* MIMEType: application/x-smalltalk-source
*
* ST/X startup configuration file:
*
* This file used to define keyboard mapping. Mappings have been moved to
*
* DeviceWorkstation class>>defaultKeyboardMapDefinition
*
* Eventually, this file will vanish.
*
* Put all your customizations to some `rc.d` file and or to your private
* startup script.
*"
Smalltalk fileIn:'keyboardMacros.rc'.