Instead of trying to identify all the .o files that make each target rely
on the targets own Makefile having a program.ro target that will compile
all the objects and link them into a single relocatable.
Rename each program's 'main' to '_crunched_<prog>_stub' instead of compiling
a small piece of C.
The old behaviour can be forced by specifying -O, and is also done if the
config file specifies 'objs' or 'objpaths'.
As well as simplifying the logic, this means you only get a single 'prog.ro
is up to date' message for each program during the build.
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