Experimental Physics and
Industrial Control System

[...]
I am sure you two are aware of the difference, but people not so
familiar with GNU make intricacies may be confused.

Absolutely right. No reason to talk gibberish.

Have a look at Base's PR#70 - Andrew separated out things very nicely. I am getting some progress on a Google Test for EPICS integration which now easily fits itself into the testing targets of the EPICS build system.
My original double-colon approach was minimally invasive but clearly not the best way to handle this.

NB. Ran into a minor bug in make (4.2.1): if you're defining multiple grouped target rules (that use the '&:' separator), make creates bogus warnings about "overriding recipe for target '&'" - the rules work fine, though.

Cheers,
~Ralph