Separating GateKeeperProxy declaration in header

Adding gatekeeperd.h and moving declarations for GateKeeperProxy into
header. Adding separate main.cpp for entry point.
Adding cc_default to be used by binary and fuzzer.
This is needed in order to fuzz gatekeeperd AIDL service

Test: m gatekeeperd
Bug: N/A
Change-Id: Ifb2082f68bb200e4ed83608a6def8e45032753de
diff --git a/gatekeeperd/main.cpp b/gatekeeperd/main.cpp
new file mode 100644
index 0000000..a05584a
--- /dev/null
+++ b/gatekeeperd/main.cpp
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <binder/IPCThreadState.h>
+#include <binder/IServiceManager.h>
+
+#include <log/log.h>
+
+#include "gatekeeperd.h"
+
+int main(int argc, char* argv[]) {
+    ALOGI("Starting gatekeeperd...");
+    if (argc < 2) {
+        ALOGE("A directory must be specified!");
+        return 1;
+    }
+    if (chdir(argv[1]) == -1) {
+        ALOGE("chdir: %s: %s", argv[1], strerror(errno));
+        return 1;
+    }
+
+    android::sp<android::IServiceManager> sm = android::defaultServiceManager();
+    android::sp<android::GateKeeperProxy> proxy = new android::GateKeeperProxy();
+    android::status_t ret = sm->addService(
+            android::String16("android.service.gatekeeper.IGateKeeperService"), proxy);
+    if (ret != android::OK) {
+        ALOGE("Couldn't register binder service!");
+        return -1;
+    }
+
+    /*
+     * We're the only thread in existence, so we're just going to process
+     * Binder transaction as a single-threaded program.
+     */
+    android::IPCThreadState::self()->joinThreadPool();
+    return 0;
+}