[Wconversion] Suppress warnings

Bug: 56258
Bug: 58162
Change-Id: I7775fb5b425dcf4d0d6ea73edfdb681eb7cb86c5
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/zlib/+/425954
Reviewed-by: Petr Hosek <phosek@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 7cc8291..bd6d517 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -158,5 +158,6 @@
   ]
 
   deps = [ ":zlib" ]
+  configs += [ ":zlib_warnings" ]
   public_configs = [ ":zlib_config" ]
 }