tests/riotboot: avoid compilation during test

- Use .bin instead of .elf since those are the actual files
  use for testing.

makefiles/boot/riotboot.mk

@@ -46,11 +46,6 @@ $(BINDIR_APP)-slot1.elf: FW_ROM_LEN=$$((SLOT1_LEN - $(RIOTBOOT_HDR_LEN)))
 $(BINDIR_APP)-slot1.elf: ROM_OFFSET=$(SLOT1_IMAGE_OFFSET)
 SLOT_RIOT_ELFS = $(BINDIR_APP)-slot0.elf $(BINDIR_APP)-slot1.elf
 
-# ensure both slot elf files are always linked
-# this ensures that both "make test" and "make test-murdock" can rely on them
-# being present without having to trigger re-compilation.
-BUILD_FILES += $(SLOT_RIOT_ELFS)
-
 # Create binary target with RIOT header
 $(SLOT_RIOT_BINS): %.$(APP_VER).riot.bin: %.hdr %.bin
 	@echo "creating $@..."

tests/riotboot/Makefile

@@ -21,11 +21,21 @@ QUIET ?= 1
 # Thus default to that (instead of epoch set by makefiles/boot/riotboot.inc.mk).
 APP_VER?=0
 
+# To avoid compilation during the test ensure both slot bin files are always
+# generated and linked this ensures that "BUILD_IN_DOCKER=1 make test" 
+# can rely on them being present without having to trigger re-compilation.
+BUILD_FILES += $(SLOT_RIOT_BINS)
+
+# To avoid compilation during the test ensure both slot elf files are always
+# generated and linked this ensures that "make test-murdock"
+# can rely on them being present without having to trigger re-compilation.
+BUILD_FILES += $(SLOT_RIOT_ELFS)
+
 # The test needs the linked slot binaries without header in order to be able to
 # create final binaries with specific APP_VER values. The CI RasPi test workers
 # don't compile themselves, thus add the required files here so they will be
 # submitted along with the test jobs.
-TEST_EXTRA_FILES=$(SLOT_RIOT_ELFS)
+TEST_EXTRA_FILES += $(SLOT_RIOT_ELFS)
 
 include ../Makefile.tests_common
 include $(RIOTBASE)/Makefile.include