Now changes in top-Makefile, middle-Makefile will result in a correct
recompiling, as it's expected:
  [criu]$ touch criu/Makefile
  [criu]$ make
  <...>
    DEP      criu/arch/x86/sigframe.d
    DEP      criu/arch/x86/sigaction_compat.d
    DEP      criu/arch/x86/crtools.d
    DEP      criu/arch/x86/cpu.d
    DEP      criu/arch/x86/call32.d
    CC       criu/arch/x86/call32.o
    CC       criu/arch/x86/cpu.o
    CC       criu/arch/x86/crtools.o
  <...>

travis-ci: success for Fix rebuild on Makefile changes
Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>