make : add new target for test binaries (#2244)

Programs in the tests directory are now build with target tests
and placed in the same location.

* clean target was expanded to remove new binaries

* test target binaries are listed in a variable

* Locations of binaries were added to the .gitignore

Signed-off-by: Jiri Podivin <jpodivin@gmail.com>
Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>