Makefile: when building libfdt only, do not add unneeded deps

implemented originally for the QEMU consumer of libfdt.

Signed-off-by: Claudio Fontana <cfontana@suse.de>
Message-Id: <20200512103315.1926-1-cfontana@suse.de>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Makefile

@@ -176,6 +176,7 @@ endif
 
 
 ifneq ($(DEPTARGETS),)
+ifneq ($(MAKECMDGOALS),libfdt)
 -include $(DTC_OBJS:%.o=%.d)
 -include $(CONVERT_OBJS:%.o=%.d)
 -include $(FDTDUMP_OBJS:%.o=%.d)
@@ -183,6 +184,7 @@ ifneq ($(DEPTARGETS),)
 -include $(FDTPUT_OBJS:%.o=%.d)
 -include $(FDTOVERLAY_OBJS:%.o=%.d)
 endif
+endif
 
 
 
@@ -318,7 +320,9 @@ ifeq ($(NO_PYTHON),0)
 TESTS_PYLIBFDT += maybe_pylibfdt
 endif
 
+ifneq ($(MAKECMDGOALS),libfdt)
 include tests/Makefile.tests
+endif
 
 #
 # Clean rules