ppp: compile with LTO enabled

Reduces .ipk size on MIPS from 98.5k to 98k

Signed-off-by: Felix Fietkau <nbd@nbd.name>

package/network/services/ppp/Makefile

@@ -189,8 +189,8 @@ $(call Build/Configure/Default,, \
 		$(PKG_BUILD_DIR)/pppd/plugins/pppoatm/linux/
 endef
 
-TARGET_CFLAGS += -ffunction-sections -fdata-sections
-TARGET_LDFLAGS += -Wl,--gc-sections
+TARGET_CFLAGS += -ffunction-sections -fdata-sections -flto
+TARGET_LDFLAGS += -Wl,--gc-sections -flto -fuse-linker-plugin
 
 MAKE_FLAGS += COPTS="$(TARGET_CFLAGS)" \
 		PRECOMPILED_FILTER=1 \