tools: Add evmc tool main file

The evmc tool can just print help and version information.

CMakeLists.txt

@@ -3,6 +3,7 @@
 # Licensed under the Apache License, Version 2.0.
 
 cmake_minimum_required(VERSION 3.5)
+cmake_policy(SET CMP0074 NEW)
 
 if(TARGET evmc)
     # The evmc library has been already created (probably by other submodule).

tools/CMakeLists.txt

@@ -2,4 +2,5 @@
 # Copyright 2019 The EVMC Authors.
 # Licensed under the Apache License, Version 2.0.
 
+add_subdirectory(evmc)
 add_subdirectory(vmtester)

tools/evmc/CMakeLists.txt

@@ -0,0 +1,14 @@
+# EVMC: Ethereum Client-VM Connector API.
+# Copyright 2019 The EVMC Authors.
+# Licensed under the Apache License, Version 2.0.
+
+hunter_add_package(CLI11)
+find_package(CLI11 REQUIRED)
+
+add_executable(evmc-tool main.cpp)
+set_target_properties(evmc-tool PROPERTIES
+    OUTPUT_NAME evmc
+    RUNTIME_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/bin)
+set_source_files_properties(main.cpp PROPERTIES
+    COMPILE_DEFINITIONS PROJECT_VERSION="${PROJECT_VERSION}")
+target_link_libraries(evmc-tool PRIVATE CLI11::CLI11)

tools/evmc/main.cpp

@@ -0,0 +1,33 @@
+// EVMC: Ethereum Client-VM Connector API.
+// Copyright 2019 The EVMC Authors.
+// Licensed under the Apache License, Version 2.0.
+
+#include <CLI/CLI.hpp>
+
+int main(int argc, const char** argv)
+{
+    CLI::App app{"EVMC tool"};
+    const auto& version_flag = *app.add_flag("--version", "Print version information");
+
+    try
+    {
+        app.parse(argc, argv);
+
+        // Handle the --version flag first and exit when present.
+        if (version_flag)
+        {
+            std::cout << "EVMC tool " PROJECT_VERSION "\n";
+            return 0;
+        }
+
+        return 0;
+    }
+    catch (const CLI::ParseError& e)
+    {
+        return app.exit(e);
+    }
+    catch (...)
+    {
+        return -1;
+    }
+}