Share srcs in rust_defaults.

Test: atest -c --include-subdirs external/rust/crates
Change-Id: If48c6cda955365e82426f78d1f1268cbc9c71ca6
diff --git a/Android.bp b/Android.bp
index d09a333..9861ed1 100644
--- a/Android.bp
+++ b/Android.bp
@@ -15,6 +15,7 @@
 rust_defaults {
     name: "rustc-hash_defaults",
     crate_name: "rustc_hash",
+    srcs: ["src/lib.rs"],
     test_suites: ["general-tests"],
     auto_gen_config: true,
     edition: "2015",
@@ -27,11 +28,9 @@
 rust_test_host {
     name: "rustc-hash_host_test_src_lib",
     defaults: ["rustc-hash_defaults"],
-    srcs: ["src/lib.rs"],
 }
 
 rust_test {
     name: "rustc-hash_device_test_src_lib",
     defaults: ["rustc-hash_defaults"],
-    srcs: ["src/lib.rs"],
 }