Introduce additional rules to work around an issue (features?) in make that 
allows the generation of a product (eg one of the cling.o file) even-though 
one of its dependency (eg. etc/cling/llvm/ADT/OwningPtr.h) has not been 
actually built.  This seems to happens if the rule to make the dependency
is a pattern rule that depend on a file (eg. interpreter/llvm/inst/include/llvm/ADT/OwningPtr.h)
that does not have a specific rule but is the byproduct of another product 
create ($(LLVMLIB)).  This is fixed by adding an explicit dependency of the
byproduct (eg. interpreter/llvm/inst/include/llvm/ADT/OwningPtr.h) on 
the main product (eg $(LLVMLIB))


git-svn-id: https://root.cern.ch/svn/root/trunk@48804 27541ba8-7e3a-0410-8455-c3a389f83636