@rafie please add some details on what this is needed.

@oranagra
The direct incentive to this was building Clang sanitizer-enabled binaries (each of which requiring its own binary), and installing them into standard locations. This was easier to manage than building with a custom prefix or renaming the built artifacts (note redis-sentinal is a symlink so trivial renaming won't work).
So this basically offers another way of tweaking the build products (in addition to PREFIX) with minimal impact on the build mechanism.

@rafie What is the purpose of supporting both PROG_SUFFIX=-suffix and PROG_SUFFIX=suffix? It might be confusing for someone who's not expecting it (e.g. do PROG_SUFFIX=.something).

@yossigo I agree. Should we then remove the whole ifneq ($(PROG_SUFFIX),) thing, and let the common use case be make PROG_SUFFIX="-foo"?

Thank you @rafie!