Makefile: Fix "make install" when "make all" needs work

Makefile: Fix "make install" when "make all" needs work

Until recently, target install used to recurse into target directories
in its recipe: it ran make install in a for-loop.  Since target
install depends on target all, this trivially ensured we run the
sub-make install only after completing target all.

Commit 1338a4b "Makefile: Reuse all's recursion machinery for clean
and install" moved the target recursion to dependencies.  That's good
(the commit message explains why), but I forgot to add dependencies to
ensure make runs the sub-make install only after completing target
all.  Do that now.

Fixes: 1338a4b72659ce08eacb9de0205fe16202a22d9c
Reported-by: Mark Cave-Ayland <[email protected]>
Reported-by: Guenter Roeck <[email protected]>
Tested-by: Guenter Roeck <[email protected]>
Signed-off-by: Markus Armbruster <[email protected]>
Message-Id: <20190712055935[email protected]>
Reviewed-by: Daniel P. Berrangé <[email protected]>
Reviewed-by: Stefano Garzarella <[email protected]>
Tested-by: Mark Cave-Ayland <[email protected]>