squash! Makefile.include: remove RIOT_VERSION_OVERRIDE

Add deprecation warning.

Makefile.include

@@ -721,15 +721,16 @@ $(RIOTBUILD_CONFIG_HEADER_C): FORCE
 	$(Q)'$(RIOTTOOLS)/genconfigheader/genconfigheader.sh' $(CFLAGS_WITH_MACROS) \
 		| '$(LAZYSPONGE)' $(LAZYSPONGE_FLAGS) '$@'
 
+# Deprecate using RIOT_VERSION_OVERRIDE but currently keep the behavior
+ifneq (,$(RIOT_VERSION_OVERRIDE))
+  $(warning 'RIOT_VERSION_OVERRIDE' is deprecated, it can now be set with 'RIOT_VERSION' directly.)
+  RIOT_VERSION = $(RIOT_VERSION_OVERRIDE)
+endif
+
 # Immediate evaluation but keep CLAGS_WITH_MACROS deferred
 _CFLAGS := $(CFLAGS)
 CFLAGS_WITH_MACROS = $(_CFLAGS)
-
-ifneq (,$(RIOT_VERSION_OVERRIDE))
-  CFLAGS_WITH_MACROS += -DRIOT_VERSION=\"$(RIOT_VERSION_OVERRIDE)\"
-else
-  CFLAGS_WITH_MACROS += -DRIOT_VERSION=\"$(RIOT_VERSION)\"
-endif
+CFLAGS_WITH_MACROS += -DRIOT_VERSION=\"$(RIOT_VERSION)\"
 
 CFLAGS := $(patsubst -D%,,$(CFLAGS))
 CFLAGS := $(patsubst -U%,,$(CFLAGS))