Drop --whole-archive and static libraries

Drop --whole-archive and static libraries

Juan has contributed a cool Makefile infrastructure that enables us to drop
static libraries completely:

Move shared obj-y definitions to Makefile.objs, prefixed {common-,hw-,user-},
and link those object files directly into the executables.

Replace HWLIB by HWDIR, specifying only the directory.

Drop --whole-archive and ARLIBS in Makefiles and configure.

Drop GENERATED_HEADERS dependency in rules.mak, since this rebuilds all
common objects after generating a target-specific header; add dependency
rules to Makefile and Makefile.target instead.

v2:
- Don't try to include /config.mak for user emulators
- Changes to user object paths ("Quickfix for libuser.a drop") were obsoleted
  by "user_only: compile everything with -fpie" (Kirill A. Shutemov)

v3:
- Fix dependency modelling for tools
- Remove comment on GENERATED_HEADERS obsoleted by this patch

Signed-off-by: Andreas Färber <[email protected]>
Cc: Blue Swirl <[email protected]>
Cc: Palle Lyckegaard <[email protected]>
Cc: Ben Taylor <[email protected]>
Cc: Juan Quintela <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Signed-off-by: Blue Swirl <[email protected]>