makefiles: use memoized for EPOCH, also define for suit

APP_VER must also be defined for suit.inc.mk in case non-fw payloads
are used (e.g. no riotboot)

Use memoized so the shell call happens only if needed

makefiles/boot/riotboot.mk

@@ -18,7 +18,7 @@ $(BINDIR_RIOTBOOT): $(CLEAN)
 export SLOT0_OFFSET SLOT0_LEN SLOT1_OFFSET SLOT1_LEN
 
 # Mandatory APP_VER, set to epoch by default
-EPOCH := $(shell date +%s)
+EPOCH = $(call memoized,EPOCH,$(shell date +%s))
 APP_VER ?= $(EPOCH)
 
 # Final target for slot 0 with riot_hdr

makefiles/suit.inc.mk

@@ -4,6 +4,15 @@
 # makefiles/suit.base.inc.mk
 #
 #
+
+# Mandatory APP_VER, set to epoch by default
+EPOCH = $(call memoized,EPOCH,$(shell date +%s))
+APP_VER ?= $(EPOCH)
+
+SUIT_VENDOR ?= "riot-os.org"
+SUIT_SEQNR ?= $(APP_VER)
+SUIT_CLASS ?= $(BOARD)
+
 SUIT_COAP_BASEPATH ?= fw/$(APPLICATION)/$(BOARD)
 SUIT_COAP_SERVER ?= localhost
 SUIT_COAP_ROOT ?= coap://$(SUIT_COAP_SERVER)/$(SUIT_COAP_BASEPATH)
@@ -15,9 +24,9 @@ $(BINDIR_SUIT): $(CLEAN)
 
 #
 SUIT_MANIFEST_BASENAME ?= riot.suit
-SUIT_MANIFEST ?= $(BINDIR_SUIT)/$(SUIT_MANIFEST_BASENAME)_unsigned.$(APP_VER).bin
+SUIT_MANIFEST ?= $(BINDIR_SUIT)/$(SUIT_MANIFEST_BASENAME)_unsigned.$(SUIT_SEQNR).bin
 SUIT_MANIFEST_LATEST ?= $(BINDIR_SUIT)/$(SUIT_MANIFEST_BASENAME)_unsigned.latest.bin
-SUIT_MANIFEST_SIGNED ?= $(BINDIR_SUIT)/$(SUIT_MANIFEST_BASENAME).$(APP_VER).bin
+SUIT_MANIFEST_SIGNED ?= $(BINDIR_SUIT)/$(SUIT_MANIFEST_BASENAME).$(SUIT_SEQNR).bin
 SUIT_MANIFEST_SIGNED_LATEST ?= $(BINDIR_SUIT)/$(SUIT_MANIFEST_BASENAME).latest.bin
 
 SUIT_NOTIFY_VERSION ?= latest
@@ -26,10 +35,6 @@ SUIT_NOTIFY_MANIFEST ?= $(SUIT_MANIFEST_BASENAME).$(SUIT_NOTIFY_VERSION).bin
 # Long manifest names require more buffer space when parsing
 export CFLAGS += -DCONFIG_SOCK_URLPATH_MAXLEN=128
 
-SUIT_VENDOR ?= "riot-os.org"
-SUIT_SEQNR ?= $(APP_VER)
-SUIT_CLASS ?= $(BOARD)
-
 SUIT_MANIFEST_PAYLOADS ?= $(SLOT0_RIOT_BIN) $(SLOT1_RIOT_BIN)
 SUIT_MANIFEST_SLOTFILES ?= $(SLOT0_RIOT_BIN):$(SLOT0_OFFSET) \
                            $(SLOT1_RIOT_BIN):$(SLOT1_OFFSET)