Creates a file .taps-failed in each O.<arch> directory,
appending the name of each tapfile that has failures to it.
The testFailures script now reads the .taps-failed files
from each directory listed in .tests-failed and nicely
displays the failing tests listed in each.
Lists the directories with failed tests at the end of the build.
It is no longer necessary to use 'make -k' to see the results
of all tests after one or more failures as only the top-level
test-results recipe will generate a build error.