Include <variant>

keystore/keystore_cli_v2.cpp uses std::get_if<> from <variant>. But it
doesn't include it but relies on the indirect inclusion of
AIDL-generated header. It should include it directly.

Bug: n/a
Test: m

Change-Id: I895bcdc69f10bc9f16a4c7c37adba6eaaf892c74
diff --git a/keystore/keystore_cli_v2.cpp b/keystore/keystore_cli_v2.cpp
index 1cfb4f6..1e9126d 100644
--- a/keystore/keystore_cli_v2.cpp
+++ b/keystore/keystore_cli_v2.cpp
@@ -19,6 +19,7 @@
 #include <iostream>
 #include <memory>
 #include <string>
+#include <variant>
 #include <vector>
 
 #include <base/command_line.h>