Makefile.features: add a common file for the features parsing

This will allow sharing it between Makefile.include and
makefiles/info-global.inc.mk.

Also some common variables definition can also be moved to here.

Part of moving CPU/CPU_MODEL definition to Makefile.features to have it
available before Makefile.include.

Makefile.features

@@ -0,0 +1,3 @@
+# Process FEATURES variables
+
+include $(RIOTBOARD)/$(BOARD)/Makefile.features

Makefile.include

@@ -245,7 +245,7 @@ export PREFIX ?= $(if $(TARGET_ARCH),$(TARGET_ARCH)-)
 INCLUDES += -I$(RIOTBASE)/core/include -I$(RIOTBASE)/drivers/include -I$(RIOTBASE)/sys/include
 
 # process provided features
-include $(RIOTBOARD)/$(BOARD)/Makefile.features
+include $(RIOTBASE)/Makefile.features
 
 # mandatory includes!
 include $(RIOTMAKE)/pseudomodules.inc.mk

makefiles/info-global.inc.mk

@@ -16,7 +16,9 @@ define board_missing_features
   FEATURES_OPTIONAL := $(FEATURES_OPTIONAL_GLOBAL)
   FEATURES_MISSING  :=
   FEATURES_PROVIDED :=
-  include $$(RIOTBOARD)/$(1)/Makefile.features
+
+  include $(RIOTBASE)/Makefile.features
+
   ifdef BUILDTEST_MCU_GROUP
     ifneq ($(BUILDTEST_MCU_GROUP), $$(FEATURES_MCU_GROUP))
       BOARDS_FEATURES_MISSING += "$(1) $(BUILDTEST_MCU_GROUP)"