Address various rustc warnings

Change-Id: I61bbfcdbbbb9a4795e2c280f70903e1b66a165c9
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/tools/rust/defs.bzl b/tools/rust/defs.bzl
index 6eb2cdb..ba58294 100644
--- a/tools/rust/defs.bzl
+++ b/tools/rust/defs.bzl
@@ -17,9 +17,10 @@
         **kwargs
     )
 
-def rust_doc(target_compatible_with = ["//tools/platforms/rust:has_support"], **kwargs):
+def rust_doc(target_compatible_with = ["//tools/platforms/rust:has_support"], rustdoc_flags = ["-Dwarnings"], **kwargs):
     _rust_doc(
         target_compatible_with = target_compatible_with,
+        rustdoc_flags = rustdoc_flags,
         **kwargs
     )
 
@@ -48,8 +49,8 @@
         rust_doc(
             name = kwargs["name"] + "_doc",
             crate = kwargs["name"],
-            rustdoc_flags = ["--document-private-items"],
             target_compatible_with = ["//tools/platforms/rust:has_support"],
+            rustdoc_flags = ["--document-private-items", "-Dwarnings"],
         )
 
 def rust_test(target_compatible_with = ["//tools/platforms/rust:has_support"], rustc_flags = [], **kwargs):