touch_noise_filter: use LDFLAGS insteat of LINK_FLAGS

When I build touch_noise_filter with additional global LDFLAGS,
I found it does not take the LDFLAGS, this patch fixes this issue.

BUG=None
TEST=emerge-lumpy touch_noise_filter passes.

Change-Id: Idfc99952506b9ab6a136bf67bb8a773d4b92bd75
Reviewed-on: https://gerrit.chromium.org/gerrit/60435
Reviewed-by: Andrew de los Reyes <adlr@chromium.org>
Commit-Queue: Yunlian Jiang <yunlian@chromium.org>
Tested-by: Yunlian Jiang <yunlian@chromium.org>
diff --git a/Makefile b/Makefile
index e4ccbc6..16fd595 100644
--- a/Makefile
+++ b/Makefile
@@ -50,16 +50,16 @@
 PC_LIBS := $(shell $(PKG_CONFIG) --libs $(PC_DEPS))
 
 CXXFLAGS += $(PC_CFLAGS)
-LINK_FLAGS += $(PC_LIBS)
+LDFLAGS += $(PC_LIBS)
 
 all: $(SONAME) $(EXE)
 
 $(SONAME): $(OBJECTS)
 	$(CXX) -shared -o $@ $(OBJECTS) -Wl,-h$(SONAME:$(OBJDIR)/%=%) \
-		$(LINK_FLAGS)
+		$(LDFLAGS)
 
 $(EXE): $(OBJECTS) $(MAINOBJ)
-	$(CXX) -o $@ $(OBJECTS) $(MAINOBJ)
+	$(CXX) -o $@ $(OBJECTS) $(MAINOBJ) $(LDFLAGS)
 
 $(OBJDIR)/%.o : %.cc
 	mkdir -p $(OBJDIR) $(DEPDIR) || true