Add utility function to get block device -> mountpoints.

Bug: 73625480

Change-Id: I996580d398a1ae7323d1fcbb4a792af53f22c8f3
diff --git a/BUILD.gn b/BUILD.gn
index b562775..73b166b 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -60,6 +60,7 @@
     "src/base:base_unittests",
     "src/ipc:perfetto_ipc_unittests",
     "src/protozero:protozero_unittests",
+    "src/traced/probes/filesystem:filesystem_unittests",
     "src/tracing:tracing_unittests",
   ]
   if (is_linux || is_android) {