Add BUILD_DIRS_ALL and simplify builddirs

Introduce BUILD_DIRS_ALL that aggregates BUILD_DIRS, EXTRA_C_BUILD_DIRS, EXTRA_CPP_BUILD_DIRS and lib_gd32. Replace multiple mkdir/conditional lines with a single mkdir -p $(BUILD_DIRS_ALL), simplifying the Rules.mk builddirs target and ensuring lib_gd32 is always created.

Author: vanvught

firmware-template-gd32/lib/Rules.mk

@@ -75,11 +75,10 @@ all : builddirs $(TARGET)
 
 .PHONY: clean builddirs
 
+BUILD_DIRS_ALL := $(BUILD_DIRS) $(EXTRA_C_BUILD_DIRS) $(EXTRA_CPP_BUILD_DIRS) lib_gd32
+
 builddirs:
-	mkdir -p $(BUILD_DIRS) 
-	if [[ -n "${EXTRA_C_BUILD_DIRS}" ]]; then mkdir -p $(EXTRA_C_BUILD_DIRS); fi
-	if [[ -n "${EXTRA_CPP_BUILD_DIRS}" ]]; then mkdir -p $(EXTRA_CPP_BUILD_DIRS); fi
-	mkdir -p lib_gd32
+	mkdir -p $(BUILD_DIRS_ALL)
 
 clean:
 	rm -rf build_gd32