Find device-dependent disk stats file, and skip disk stats if not available.

Change-Id: I03afb85e3357dd4c2cf5effd98b194c71d77c71d

BUG=12171
TEST=unit tested

Review URL: http://codereview.chromium.org/6541007
diff --git a/metrics/Makefile b/metrics/Makefile
index 5e3ed14..032ea73 100644
--- a/metrics/Makefile
+++ b/metrics/Makefile
@@ -38,7 +38,8 @@
 	metrics_library_test.o
 
 TESTCOUNTER_LIBS = -lgmock -lgtest -lbase -lrt -lpthread -lglib-2.0
-DAEMON_LDFLAGS = $(LDFLAGS) $(LDCONFIG) -lrt -lbase -lpthread -lgflags -lglib-2.0
+DAEMON_LDFLAGS = $(LDFLAGS) $(LDCONFIG) -lrt -lbase -lpthread -lgflags \
+		 -lglib-2.0 -lrootdev
 TESTDAEMON_LIBS = -lgmock -lgtest
 TESTLIB_LIBS = -lgtest -lbase -lrt -lpthread -lglib-2.0