[Makefile] Add testing targets

This adds a set of code generation profiling tests which are suitable to
evaluate the time required to generate code and build some reference
programs.

Signed-off-by: Patrick Bellasi <[email protected]>

[Makefile] Bugfix libproduct dependency

Usually, the libproduct is built out of the XML descriptor generated files
and only linked with the Stesp (i.e. XTIL) libraries. This patch removes
the build dependency from the STEPS library since this lib is to be considered
pre-build and already available in binary.

Signed-off-by: Patrick Bellasi <[email protected]>