- Remove most of the step5 excludes in the Makefile except for ones
which don't have TCO capability at all (or the implementation is too
slow): bash, make, mal, matlab.
- Make perf_EXCLUDES consistent with other excludes.
- Add a print-FOO target which prints the resolved value of Makefile
variable FOO. For example, `make print-IMPLS` to print the list of
implementations.
