Add a tool to add keys to keyring.

This CL adds a binary to load keys to a keyring.

Bug: 112038861
Test: mini-keyctl -k .fsverity -c PATH_CONTAINER_CERTS
Test: cat /proc/keys and find the newly added keys
Change-Id: Iead68618ea194e9412616c5c6cff885e3cf78520
diff --git a/libkeyutils/Android.bp b/libkeyutils/Android.bp
index b388e95..e816926 100644
--- a/libkeyutils/Android.bp
+++ b/libkeyutils/Android.bp
@@ -16,3 +16,16 @@
     srcs: ["keyutils_test.cpp"],
     test_suites: ["device-tests"],
 }
+
+cc_binary {
+    name: "mini-keyctl",
+    srcs: ["mini_keyctl.cpp"],
+
+    shared_libs: [
+        "libbase",
+        "libkeyutils",
+        "liblog",
+    ],
+
+    cflags: ["-Werror", "-Wall", "-Wextra"],
+}