compile_multilib: both for libbinder RPC tests

Needed to add suffixes and update the test that relied on knowing the
path/name of binaries on device.

Test: none
Bug: 355046194
Change-Id: If1af4e5adebb6cd492639813037d236c7ef0fe8a
diff --git a/libs/binder/tests/Android.bp b/libs/binder/tests/Android.bp
index 4c7684c..dd50fbd 100644
--- a/libs/binder/tests/Android.bp
+++ b/libs/binder/tests/Android.bp
@@ -235,6 +235,16 @@
         "binder_test_defaults",
     ],
 
+    compile_multilib: "both",
+    multilib: {
+        lib32: {
+            suffix: "32",
+        },
+        lib64: {
+            suffix: "64",
+        },
+    },
+
     static_libs: [
         "libbinder_test_utils",
         "libbinder_tls_static",
@@ -267,7 +277,6 @@
     defaults: [
         "binderRpcTest_common_defaults",
     ],
-    compile_multilib: "first",
 
     srcs: [
         "binderRpcTest.cpp",