[Add] 添加测试使用：引用后再定义

.editorconfig

@@ -0,0 +1,14 @@
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+[*]
+end_of_line = lf
+charset     = utf-8
+
+[Makefile]
+indent_style = tab
+indent_size  = 8
+trim_trailing_whitespace = false
+insert_final_newline     = false

01-Variable_MAKEFILE_LIST/Makefile

@@ -1,9 +1,11 @@
 
-
 makedir := $(abspath $(lastword $(MAKEFILE_LIST)))
 $(warning makedir1=$(makedir))
 
 include dir1/Makefile
+
 makedir := $(abspath $(lastword $(MAKEFILE_LIST)))
 $(warning makedir3=$(makedir))
 
+all:
+	@echo "Completing the main Makefile"

02-Test_set_after_reference/Makefile

@@ -0,0 +1,10 @@
+
+PUBLIC_INCVPATH += $(PROJECT_ROOT)/public
+$(warning "PUBLIC_INCVPATH : $(PUBLIC_INCVPATH), with PROJECT_ROOT not set")
+
+PROJECT_ROOT:=$(CURDIR)
+
+$(warning "PUBLIC_INCVPATH : $(PUBLIC_INCVPATH), with PROJECT_ROOT set")
+
+all:
+	@echo "This is a dummy target to ensure the Makefile is valid."