tslib: use more robust $@ when touching target instead of explisit name

package/tslib/tslib.mk

@@ -17,7 +17,7 @@ tslib-source: $(DL_DIR)/$(TSLIB_SOURCE)
 $(TSLIB_DIR)/.patched: $(DL_DIR)/$(TSLIB_SOURCE)
 	$(TSLIB_CAT) $(DL_DIR)/$(TSLIB_SOURCE) | tar -C $(BUILD_DIR) $(TAR_OPTIONS) -
 	toolchain/patch-kernel.sh $(TSLIB_DIR) package/tslib/ tslib\*.patch
-	touch $(TSLIB_DIR)/.patched
+	touch $@
 
 $(TSLIB_DIR)/.configured: $(TSLIB_DIR)/.patched
 	(cd $(TSLIB_DIR); rm -rf config.cache; ./autogen.sh)
@@ -47,11 +47,11 @@ $(TSLIB_DIR)/.configured: $(TSLIB_DIR)/.patched
 	--enable-input \
 	)
 	$(SED) 's:rpl\_malloc:malloc:g' $(TSLIB_DIR)/config.h
-	touch $(TSLIB_DIR)/.configured
+	touch $@
 
 $(TSLIB_DIR)/.compiled: $(TSLIB_DIR)/.configured
 	$(MAKE) -C $(TSLIB_DIR)
-	touch $(TSLIB_DIR)/.compiled
+	touch $@
 
 $(STAGING_DIR)/usr/lib/libts.so: $(TSLIB_DIR)/.compiled
 	$(MAKE) -C $(TSLIB_DIR) \