aria2: size optimizations

Reduce binary size by about 22%

Signed-off-by: Deng Qingfang <dengqf6@mail2.sysu.edu.cn>

net/aria2/Makefile

@@ -80,6 +80,9 @@ CONFIGURE_ARGS += \
 	--without-libuv \
 	--with-libz
 
+TARGET_CXXFLAGS += -ffunction-sections -fdata-sections -flto
+TARGET_LDFLAGS += -Wl,--gc-sections -flto
+
 define Package/aria2/install
 	$(INSTALL_DIR) $(1)/usr/bin
 	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/bin/aria2c $(1)/usr/bin