Rebuilding targets when configurations change

In situations where configuration changes necessitate a rebuild of
dependencies, such as due to feature modifications, these targets must
be dependent on the build system itself. While this approach may not
always be perfect, it ensures that we avoid using outdated artifacts
in our builds.

To enhance this process, we no longer rely on file timestamps but
instead base dependencies on configurations. The relevant file is
generated by a rule that always executes, but the target will only be
updated if there are actual changes to the configuration content.
This approach ensures that only substantial content alterations trigger
an update to the file's timestamp.

Makefile

@@ -123,10 +123,19 @@ $(BIN): $(OBJS)
 	$(VECHO) "  LD\t$@\n"
 	$(Q)$(CC) -o $@ $^ $(LDFLAGS)
 
+clean-generated-files = \
+	$(RM) $(BIN) $(OBJS) $(HIST_BIN) $(HIST_OBJS) $(deps) $(CACHE_OUT)
+
 .PHONY: config
 config:
-	$(Q)echo "$(CFLAGS)" | xargs -n1 | sort | sed -n 's/^RV32_FEATURE/ENABLE/p' > $(CONFIG_FILE)
-	$(VECHO) "Check the file $(OUT)/.config for configured items.\n"
+	$(Q)echo "$(CFLAGS)" | xargs -n1 | sort | sed -n 's/^RV32_FEATURE/ENABLE/p' > $(CONFIG_FILE).tmp
+	$(Q)cmp -s $(CONFIG_FILE) $(CONFIG_FILE).tmp; \
+	    RETVAL=$$?; \
+	    if [ $$RETVAL -ne 0 ]; then \
+	    mv -f $(CONFIG_FILE).tmp $(CONFIG_FILE); \
+	    $(call clean-generated-files); \
+	    $(PRINTF) "Check the file $(OUT)/.config for configured items.\n\n"; \
+	    fi
 
 # Tools
 include mk/tools.mk
@@ -160,10 +169,10 @@ EXPECTED_aes = Dec 15 2022 16:35:12 Test results AES-128 ECB encryption: PASSED!
 misalign: $(BIN)
 	$(Q)$(PRINTF) "Running aes.elf ... "; 
 	$(Q)if [ "$(shell $(BIN) -m $(OUT)/aes.elf | uniq)" = "$(EXPECTED_aes)" ]; then \
-        $(call notice, [OK]); \
-	else	\
-        $(PRINTF) "Failed.\n"; \
-    fi
+	    $(call notice, [OK]); \
+	    else \
+	    $(PRINTF) "Failed.\n"; \
+	    fi
 
 include mk/external.mk
 
@@ -178,7 +187,7 @@ endif
 endif
 
 clean:
-	$(RM) $(BIN) $(OBJS) $(HIST_BIN) $(HIST_OBJS) $(deps) $(CACHE_OUT)
+	$(Q)$(call clean-generated-files)
 distclean: clean
 	-$(RM) $(DOOM_DATA) $(QUAKE_DATA)
 	$(RM) -r $(OUT)/id1

mk/riscv-arch-test.mk

@@ -11,6 +11,6 @@ endif
 	git submodule update --init $(dir $(ARCH_TEST_DIR))
 	$(Q)python3 -B $(RISCV_TARGET)/setup.py --riscv_device=$(RISCV_DEVICE)
 	$(Q)riscof run --work-dir=$(WORK) \
-			--config=$(RISCV_TARGET)/config.ini \
-			--suite=$(ARCH_TEST_DIR)/riscv-test-suite \
-	   		--env=$(ARCH_TEST_DIR)/riscv-test-suite/env
+	               --config=$(RISCV_TARGET)/config.ini \
+	               --suite=$(ARCH_TEST_DIR)/riscv-test-suite \
+	               --env=$(ARCH_TEST_DIR)/riscv-test-suite/env