Build with mls_build_async

This switches the API to use async Rust throughout. We need async APIs
for the Jetpack library.

Bug: 337838209
Test: Presubmit
Change-Id: I4ae676a65a3c95acb123f916052996b5e37f5051
diff --git a/Android.bp b/Android.bp
index 070c877..2e98795 100644
--- a/Android.bp
+++ b/Android.bp
@@ -36,13 +36,20 @@
         "std",
         "x509",
     ],
+    cfgs: [
+        "mls_build_async",
+        "mls_build_async",
+    ],
     rustlibs: [
         "libhex",
         "libmls_rs_codec",
         "libthiserror",
         "libzeroize",
     ],
-    proc_macros: ["libmaybe_async"],
+    proc_macros: [
+        "libasync_trait",
+        "libmaybe_async",
+    ],
     apex_available: [
         "//apex_available:platform",
         "//apex_available:anyapex",
diff --git a/cargo_embargo.json b/cargo_embargo.json
index cb908d7..2a253ec 100644
--- a/cargo_embargo.json
+++ b/cargo_embargo.json
@@ -1,3 +1,3 @@
 {
-  "run_cargo": false
+    "extra_cfg": ["mls_build_async"]
 }