Alter FileReader's memory management

Make it so that the FileReader allows control of the memory before
at the callsite rather than over the whole lifetime of the FileReader
object.

Change-Id: Iee418af8dfa014dcf9718e9cff549ae69e5bc569
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/aos/util/BUILD b/aos/util/BUILD
index 929b376..2f10a70 100644
--- a/aos/util/BUILD
+++ b/aos/util/BUILD
@@ -346,6 +346,7 @@
     target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/scoped:scoped_fd",
+        "@com_github_google_flatbuffers//:flatbuffers",
         "@com_github_google_glog//:glog",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/types:span",