makefile: fix not install ngxvar dir (#9)

Signed-off-by: Vinson Zou <vinsonzou@users.noreply.github.com>

Author: vinsonzou

Makefile

@@ -10,7 +10,9 @@ test = t/
 .PHONY: all test install
 
 install:
-	$(INSTALL) -m664 lib/resty/*.lua $(DESTDIR)$(LUA_LIB_DIR)/resty
+	$(INSTALL) -d $(DESTDIR)$(LUA_LIB_DIR)/resty/ngxvar/
+	$(INSTALL) -m664 lib/resty/ngxvar/*.lua $(DESTDIR)$(LUA_LIB_DIR)/resty/ngxvar/
+	$(INSTALL) -m664 lib/resty/*.lua $(DESTDIR)$(LUA_LIB_DIR)/resty/
 
 test:
 	PATH=$(OPENRESTY_PREFIX)/nginx/sbin:$$PATH prove -I../test-nginx/lib -r $(test)