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/Android.bp b/gatekeeperd/Android.bp
index 838f734..145a74c 100644
--- a/gatekeeperd/Android.bp
+++ b/gatekeeperd/Android.bp
@@ -18,8 +18,8 @@
     default_applicable_licenses: ["Android-Apache-2.0"],
 }
 
-cc_binary {
-    name: "gatekeeperd",
+cc_defaults {
+    name: "gatekeeperd_defaults",
     cflags: [
         "-Wall",
         "-Wextra",
@@ -52,6 +52,16 @@
 
     static_libs: ["libscrypt_static"],
     include_dirs: ["external/scrypt/lib/crypto"],
+}
+
+cc_binary {
+    name: "gatekeeperd",
+    defaults: [
+        "gatekeeperd_defaults",
+    ],
+    srcs: [
+        "main.cpp",
+    ],
     init_rc: ["gatekeeperd.rc"],
 }