[Tf-a-tests] tests_list.h compiling problem

Hi developers,

There is a Makefile dependency problem regarding the "tests_list.h" as it mentioned in https://git.trustedfirmware.org/TF-A/tf-a-tests.git/tree/docs/change-log.rst

I have a fix to that (in one way) but not perfect: https://github.com/AlamyLiu/tf-a-tests/commit/33929aca35c7ad65e9acde71260595...

I think the root cause is that

* It uses `eval` in Makefile to `do` the job that should be done by `make`. * Makefile should have only the `rules` (none), not the action (verb - eval) for compiling.

Using `eval` to compile the code hide the information to `make`. Let `make` know the rules & dependency so the problem could be solved cleanly.

P.S.: The workaround is `make -j1`. Which has self-described the dependency problem.

Regards, Alamy