modules/dasharo-ec: fix build system and address review feedback

- Remove leading tabs from ifeq variable assignments (Make parse error)
- Move post-build steps (cp, dd, touch) out of dasharo-ec_target into
  a proper Make rule; _target is now only make arguments
- Set dasharo-ec_output to ec.rom (the actual artifact, not .built)
- Add -$(BOARD) suffix to dasharo-ec_base_dir and dasharo-ec_dir so
  v540tu and v560tu maintain independent build trees and ec.rom files
- Add explicit rule to copy and zero-pad ec.rom to 128 KB
- Fix coreboot copy rule: use FORCE + cmp so the recipe always runs
  but only updates the destination (and its mtime) when content differs,
  preventing the mtime race between boards sharing coreboot_base_dir

Signed-off-by: Filip Lewiński <filip.lewinski@3mdeb.com>

Author: filipleple

modules/dasharo-ec

@@ -7,42 +7,45 @@ dasharo-ec_commit_hash := d198b641195e60e13afc17be9464e4f402d1c2fa
 
 # Map BOARD to the EC board model
 ifeq "$(BOARD)" "novacustom-v540tu"
-	DASHARO_EC_BOARD_MODEL := v540tu
+DASHARO_EC_BOARD_MODEL := v540tu
 else ifeq "$(BOARD)" "novacustom-v560tu"
-	DASHARO_EC_BOARD_MODEL := v560tu
+DASHARO_EC_BOARD_MODEL := v560tu
 else
-	$(error "$(BOARD): no Dasharo EC board model mapping defined")
+$(error "$(BOARD): no Dasharo EC board model mapping defined")
 endif
 
 dasharo-ec_version := $(dasharo-ec_commit_hash)
-dasharo-ec_base_dir := dasharo-ec-$(dasharo-ec_version)
-dasharo-ec_dir := dasharo-ec-$(dasharo-ec_version)
+dasharo-ec_base_dir := dasharo-ec-$(dasharo-ec_version)-$(BOARD)
+dasharo-ec_dir := dasharo-ec-$(dasharo-ec_version)-$(BOARD)
 
-# Use .built sentinel since the real output is in a dynamic path
-dasharo-ec_output := .built
+# ec.rom is copied to a stable path by the explicit rule below
+dasharo-ec_output := ec.rom
 
 # No-op configure: submodules are handled by the EC Makefile's canary rule
 # for git repos
 dasharo-ec_configure :=
 
-# Build the EC firmware following the upstream build.sh process:
-#  1. make BOARD=novacustom/<model>  (compile with SDCC)
-#  2. Copy ec.rom from the dynamic output path to a known location
-#  3. Extend ec.rom to 128KB (zero-padded) as required by coreboot
-# Note: the && chain after make -C runs in the parent cwd, so use
-# absolute paths.  Use sh -c so the shell expands the glob.
-dasharo-ec_target := \
-	BOARD=novacustom/$(DASHARO_EC_BOARD_MODEL) \
-	&& sh -c 'cp $(build)/$(dasharo-ec_dir)/build/novacustom/$(DASHARO_EC_BOARD_MODEL)/*/ec.rom $(build)/$(dasharo-ec_dir)/ec.rom' \
-	&& dd if=/dev/zero of=$(build)/$(dasharo-ec_dir)/ec.rom bs=1 seek=128k count=0 \
-	&& touch $(build)/$(dasharo-ec_dir)/.built
-
-# Copy ec.rom into the coreboot source tree before coreboot configures.
-# coreboot expects ec.rom in its root directory.
-$(build)/$(coreboot_base_dir)/ec.rom: $(build)/$(dasharo-ec_dir)/.build
-	$(call do,COPY,ec.rom -> coreboot, \
-		cp "$(build)/$(dasharo-ec_dir)/ec.rom" "$@" \
-	)
+# Build the EC firmware: only pass make arguments; post-build steps are
+# handled by the explicit rule below.
+dasharo-ec_target := BOARD=novacustom/$(DASHARO_EC_BOARD_MODEL)
+
+# Copy ec.rom from the dynamic build path to a stable location and pad to
+# 128KB as required by coreboot. Runs after the module make completes.
+$(build)/$(dasharo-ec_dir)/ec.rom: $(build)/$(dasharo-ec_dir)/.build
+	sh -c 'cp $(build)/$(dasharo-ec_dir)/build/novacustom/$(DASHARO_EC_BOARD_MODEL)/*/ec.rom $@'
+	dd if=/dev/zero of=$@ bs=1 seek=128k count=0
+
+# Copy ec.rom into the coreboot source tree before coreboot builds.
+# coreboot_base_dir (coreboot-dasharo) is shared between v540tu and v560tu, so
+# a plain timestamp-based rule is racy: whichever board built last wins the mtime
+# race and the other board silently keeps the wrong binary.  Adding FORCE makes the
+# recipe always run so we can do a content check; the actual cp (and the mtime
+# update that triggers downstream rebuilds) only happens when the content differs.
+$(build)/$(coreboot_base_dir)/ec.rom: $(build)/$(dasharo-ec_dir)/ec.rom FORCE
+	@if ! cmp -s "$(build)/$(dasharo-ec_dir)/ec.rom" "$@" 2>/dev/null; then \
+		echo "$(DATE) COPY $(DASHARO_EC_BOARD_MODEL) ec.rom -> coreboot"; \
+		cp "$(build)/$(dasharo-ec_dir)/ec.rom" "$@"; \
+	fi
 
 # Ensure coreboot's configure step depends on ec.rom being present
 $(build)/$(coreboot_dir)/.configured: $(build)/$(coreboot_base_dir)/ec.rom