Supporting changes for Add limited sandbox capability to "make check"
Non-tests/... changes:
- Add HAS_TESTS= to Makefiles with libraries and programs to enable iteration and propagate the appropriate environment down to *.test.mk.
tests/... changes:
- Add appropriate support Makefile.inc's to set HAS_TESTS in a minimal manner, since tests/... is a special subdirectory tree compared to the others.
MFC after: 2 months
MFC with: rXXXXXXX
Requested by: jhb