Makefile: fix clean and distclean for external libs.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

external/Makefile

@@ -100,13 +100,13 @@ clean: external-clean
 
 external-clean:
 	$(RM) $(EXTERNAL_LIBS) $(TARGET_DIR)/*.la $(TARGET_DIR)/*.o
+	$(RM) $(TARGET_DIR)/jsmn-build/jsmn.o
 	if [ -f ${TARGET_DIR}/libsodium-build/Makefile ]; then make -C ${TARGET_DIR}/libsodium-build clean; fi
 	if [ -f ${TARGET_DIR}/libwally-core-build/Makefile ]; then make -C ${TARGET_DIR}/libwally-core-build clean; fi
 	if [ -f ${TARGET_DIR}/libwally-core-build/src/Makefile ]; then make -C ${TARGET_DIR}/libwally-core-build/src clean; fi
+	if [ -f ${TARGET_DIR}/libacktrace-build/Makefile ]; then make -C ${TARGET_DIR}/libbacktrace-build/src clean; fi
 
 external-distclean:
 	make -C external/libsodium distclean || true
-	$(RM) -rf ${TARGET_DIR}/libbacktrace-build
-	$(RM) ${TARGET_DIR}/libsodium-build/src/libsodium/libsodium.la
-	$(RM) ${TARGET_DIR}/libwally-core-build/src/secp256k1/libsecp256k1.la ${TARGET_DIR}/libwally-core-build/src/libwallycore.la
+	$(RM) -rf ${TARGET_DIR}/libbacktrace-build ${TARGET_DIR}/libsodium-build ${TARGET_DIR}/libwally-core-build ${TARGET_DIR}/jsmn-build
 	$(RM) -r `git status --ignored --porcelain external/libwally-core | grep '^!! ' | cut -c3-`