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.
(Smalltalk at:#stx_goodies_smallsense) notNil ifTrue:[
(Smalltalk at:#stx_goodies_smallsense) swizzle.
UserPreferences default
smallSenseEnabled: true;
smallSenseBackgroundLintEnabled: true;
smallSenseBackgroundTypingEnabled: true;
smallSenseNewDialogsEnabled: true;
smallSenseCompletionEnabled: true.
].