[Wconversion] Suppress warnings

Bug: 58162
Change-Id: I8245e5e2265de147699a20595f8437d153bd077a
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/openssl-ecjpake/+/426270
Reviewed-by: Petr Hosek <phosek@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index cf0149c..9c4b629 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -13,7 +13,6 @@
   public_configs = [ ":openssl-ecjpake_config" ]
   deps = [ "//third_party/boringssl" ]
   # Suppress warnings in upstream code that are triggered by Fuchsia compilation flags.
-  cflags = [ "-Wno-conversion" ]
 }
 
 config("openssl-ecjpake_config") {
@@ -21,6 +20,8 @@
     ".",
     "openssl",
   ]
+  cflags = [ "-Wno-conversion" ]
+  visibility = [ ":*" ]
 }
 
 executable("openssl-ecjpake_test") {