add assimp target as depndency for examples

Makefile

@@ -21,6 +21,7 @@ ifeq ($(USE_INTERNAL_ASSIMP), y)
 CXXFLAGS += -I$(ASSIMP_DIR)/include
 ASSIMP_LIB := $(ASSIMP_DIR)/build/code/libassimp.a
 BUILD_ASSIMP_TARGET := build_assimp
+CLEAN_ASSIMP_TARGET := $(MAKE) -C $(ASSIMP_DIR)/build clean
 endif
 
 
@@ -55,11 +56,12 @@ $(LIBNAME): $(RENDER_OBJECTS)
 $(RENDER_OBJECTS): $(OBJDIR)/%.o : $(SRCDIR)/%.cpp
 	$(CXX) $(CXXFLAGS) -c -MMD $< -o $@
 
-examples: $(LIBNAME)
+examples: $(LIBNAME) $(BUILD_ASSIMP_TARGET)
 	ASSIMP_DIR=$(ASSIMP_DIR) $(MAKE) -C $(EXAMPLEDIR)
 .PHONY: examples
 
 clean:
 	rm -rf $(OBJDIR)/*
 	$(MAKE) clean -C $(EXAMPLEDIR)
+	$(CLEAN_ASSIMP_TARGET)
 .PHONY: clean