refactor(make): reorganize targets and improve locking mechanism

1.	Introduce a “project lock” mechanism alongside the existing “build lock”; the lock file is now generated within the platform-specific Makefile.
2.	Set `project` as the default Makefile goal for consistency.
3.	Remove the `standalone` target to improve compatibility, especially when invoked via `make -f`.
4.	Simplify target dependencies for better maintainability and clarity.

platform/xilinx/xilinx.mk

@@ -7,6 +7,8 @@ define tcl_util
 		 $(CONFIG_FILE) $(BUILD_DIR)
 endef
 
+PHONY += xilinx_reset xilinx_project xilinx_sdkclean xilinx_sdkbuild
+
 xilinx_sdkopen:
 	@$(call log,Launching IDE...)
 	@if [ "$(call check_command,vitis)" = "y" ]; then \
@@ -21,19 +23,22 @@ xilinx_sdkopen:
 		echo "No IDE found!" && exit 1; \
 	fi
 
-PHONY += xilinx_sdkbuild
 xilinx_sdkbuild:
 	@$(call log,[Build] SDK projects in $(BUILD_DIR))
 	$(call tcl_util, build) $(HIDE)
+	@echo "$(TIMESTAMP): Build lock." > $(BUILD_LOCK)
 
 xilinx_sdkclean:
 	@$(call log,[Delete] SDK artefacts from $(BUILD_DIR))
 	$(call tcl_util, clean_project) $(HIDE)
 
-xilinx_project:
-	@$(call print,Creating and configuring the IDE project)
-	$(call mk_dir,$(BUILD_DIR))
+$(XILINX_PROJECT_LOCK):
+	@$(call log,Creating and configuring the IDE project)
+	@$(call cmd_mkdir,$(BUILD_DIR))
 	$(call tcl_util, create_project) $(HIDE)
+	@echo "$(TIMESTAMP): Project lock." > $@
+
+xilinx_project: $(PROJECT_LOCK)
 
 xilinx_reset:
 	$(call cmd_remove,.Xil) $(HIDE)