hello-cpp: init

Proposal: a trivial hello-cpp to complement gnu hello, testing C++ and
cmake infrastructure.

This is intended to assist with testing exotic stdenvs such as the one
used in pkgsLLVM, requiring no additional dependencies to get a quick
test that the compiler and cmake are working as intended as a basic
level.

There does already exist tests.cc-wrapper, but this does not produce any
outputs, and sometimes it is useful to have a quick test that something
builds. It's also useful to be able to inspect the outputs to look at
references and so forth.

Signed-off-by: Peter Waller <[e-mail]>

pkgs/by-name/he/hello-cpp/package.nix

···
+{
+  cmake,
+  lib,
+  ninja,
+  stdenv,
+}:
+
+stdenv.mkDerivation {
+  name = "hello-cpp";
+  src = ./src;
+  nativeBuildInputs = [ cmake ninja ];
+  meta = {
+    description = "Basic sanity check that C++ and cmake infrastructure are working";
+    platforms = lib.platforms.all;
+    maintainers = stdenv.meta.maintainers or [];
+    mainProgram = "hello-cpp";
+  };
+}

pkgs/by-name/he/hello-cpp/src/CMakeLists.txt

···
+cmake_minimum_required(VERSION 3.10)
+project(hello-cpp)
+
+add_executable(hello-cpp main.cpp)
+
+install(TARGETS hello-cpp)

pkgs/by-name/he/hello-cpp/src/main.cpp

···
+#include <iostream>
+
+int main(int argc, char *argv[]) {
+    std::cout << "Hello, C++\n";
+    return 0;
+}