Use header rather than forward declaration.

We can do this now the header is exported.

Test: Still builds.
Change-Id: Ic5176346ec66395957cb4d34fb02be011587e50f
diff --git a/compos/compos_key_cmd/Android.bp b/compos/compos_key_cmd/Android.bp
index e0584f4..36c1b5c 100644
--- a/compos/compos_key_cmd/Android.bp
+++ b/compos/compos_key_cmd/Android.bp
@@ -15,8 +15,8 @@
         "android.system.virtualizationservice-ndk",
         "compos_aidl_interface-ndk",
         "libbase",
-        "libbinder_rpc_unstable",
         "libbinder_ndk",
+        "libbinder_rpc_unstable",
         "libcrypto",
         "libfsverity",
         "libprotobuf-cpp-lite",
diff --git a/compos/compos_key_cmd/compos_key_cmd.cpp b/compos/compos_key_cmd/compos_key_cmd.cpp
index eb11d92..ff53548 100644
--- a/compos/compos_key_cmd/compos_key_cmd.cpp
+++ b/compos/compos_key_cmd/compos_key_cmd.cpp
@@ -33,6 +33,7 @@
 #include <openssl/x509.h>
 #include <unistd.h>
 
+#include <binder_rpc_unstable.hpp>
 #include <chrono>
 #include <condition_variable>
 #include <filesystem>
@@ -43,11 +44,6 @@
 
 #include "compos_signature.pb.h"
 
-// From frameworks/native/libs/binder/rust/src/binder_rpc_unstable.hpp
-extern "C" {
-AIBinder* RpcClient(unsigned int cid, unsigned int port);
-}
-
 using namespace std::literals;
 
 using aidl::android::system::virtualizationservice::BnVirtualMachineCallback;