Generate dependencies when compiling the .o

If we don't have a .o, we don't need dependencies, so skip the setup
step of building them. Instead, when building the .o, we generate the
.dep and output it (to objs/ to make the rules a little easier). The
next run of make will include the dep file and any dependencies will be
picked up.

This change also disables the disabling of dependency checking if we
have zlib or openssl being compiled from third_party. Additionally it
inverts the logic for including dependencies from ONLY if we are doing a
clean to ONLY if we are NOT doing a clean.
2 files changed