Unlike with the doxygen source generation, we can't autoguess which of
the class files are eligible automatically. Instead, make a stub hid
file, (which we can now start adding to, if desired) and include it in
all builds that include other class stubs.
The leading - makes it rather inconsistent with the majority of other
projects around the world. Use the form everyone else uses.
To solve this, properly pass prefix to inner makes as was always
intended.
Fixes: https://github.com/libopencm3/libopencm3/issues/1058
Somewhat replaces some earlier work done by hg/lg, but much more
complete, so we kept it as is, because it's bringing in even more parts
after this.
Reviewed-by: Karl Palsson <karlp@tweak.net.au>
