update makefiles to not always rebuild archive

Makefile

@@ -24,11 +24,10 @@ CLEAN_ASSIMP_TARGET := $(MAKE) -C $(ASSIMP_DIR)/build clean
 endif
 
 
-all: mkdirs
+all: mkdirs $(LIBNAME)
 ifeq ($(USE_INTERNAL_ASSIMP), y)
 	$(MAKE) $(ASSIMP_LIB)
 endif
-	$(MAKE) $(LIBNAME)
 	$(MAKE) examples
 .PHONY: all
 
@@ -54,7 +53,7 @@ mkdirs:
 .PHONY: mkdirs
 
 $(LIBNAME): $(RENDER_OBJECTS)
-	ar -crs $(OBJDIR)/$(LIBNAME) $(RENDER_OBJECTS)
+	ar -crsuU $(OBJDIR)/$(LIBNAME) $(RENDER_OBJECTS)
 
 $(RENDER_OBJECTS): $(OBJDIR)/%.o : $(SRCDIR)/%.cpp
 	$(CXX) $(CXXFLAGS) -c -MMD $< -o $@

examples/Makefile

@@ -15,7 +15,7 @@ endif
 
 EXAMPLE_SOURCES = \
 	render_groups/main.cpp \
-	assimp_loading/main.cpp
+	#assimp_loading/main.cpp
 	#hello_world/main.cpp \
 	#simple_mesh/main.cpp
 EXAMPLE_OBJECTS = $(patsubst %/, $(OBJDIR)/%.o, $(dir $(EXAMPLE_SOURCES)))
@@ -24,7 +24,7 @@ all: mkdirs $(EXAMPLE_OBJECTS)
 
 -include $(OBJDIR)/*.d
 
-$(EXAMPLE_OBJECTS):
+$(EXAMPLE_OBJECTS): $(LIB)
 	$(CXX) $(CXXFLAGS) -c -MMD $(basename $(notdir $@))/main.cpp -o $@
 	$(CXX) -o $(BINDIR)/$(notdir $(basename $@)) $(LDFLAGS) $@ $(LIB) \
 		$(ASSIMP_LIB)