ppp: use --gc-sections to save a tiny bit of space

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

package/network/services/ppp/Makefile

@@ -172,6 +172,9 @@ $(call Build/Configure/Default,, \
 		$(PKG_BUILD_DIR)/pppd/plugins/pppoatm/linux/
 endef
 
+TARGET_CFLAGS += -ffunction-sections -fdata-sections
+TARGET_LDFLAGS += -Wl,--gc-sections
+
 MAKE_FLAGS += COPTS="$(TARGET_CFLAGS)" \
 		PRECOMPILED_FILTER=1 \
 		STAGING_DIR="$(STAGING_DIR)"