Certain redo post-build failures would still mark a target as built.

If we failed because:
- target dir doesn't exist
- failed to copy from stdout
- failed to rename $3

We would correctly return error 209, but the target would still be
marked as having been built, so redo-ifchange would not try to build it
next time, beause we forgot to call sf.set_failed() in those cases.

minimal/do worked correctly.

Added a test to catch this in the future.

t/122-defaults-parent/clean.do

@@ -0,0 +1,2 @@
+rm -f *~ .*~ */*~ */.*~ *.tmp */*.tmp x/shouldfail *.log */*.log
+