Review for 7141244: build-infra merge: Include $(SPEC) in makefiles and make variables overridable

[Fredrik Öhrström]

----- david.holmes at oracle.com skrev: 
> This reminded me that one of the things on my wishlist for the new
> build 
> was that I can still override something in SPEC by setting it on the 
> command-line invocation of make.

That should work, since a variable specified on the make command line, 
forcibly overrides any attempt to set it inside the makefiles.
(Well, you can forcibly-forcibly override it again in the makefile, but
we have no intention to do that.)

We only need to make sure that the variables specified to the
root makefile gets propagated to the sub-make command lines. 
Should be easy to fix.

But it will not be part of this webrev. 

//Fredrik