Also print Rust-side features/cfg in rpm-ostree --version

Let's make it obvious whether the `fedora-infrastructure` feature
is compiled in.

rust/src/lib.rs

@@ -84,6 +84,7 @@ mod ffi {
     // utils.rs
     extern "Rust" {
         fn varsubstitute(s: &str, vars: &Vec<StringMapping>) -> Result<String>;
+        fn get_features() -> Vec<String>;
     }
 
     #[derive(Default)]

rust/src/utils.rs

@@ -294,3 +294,10 @@ pub(crate) fn varsubstitute(s: &str, subs: &Vec<crate::ffi::StringMapping>) -> R
     let m = subs.iter().cloned().map(|i| (i.k, i.v)).collect();
     varsubst(s, &m)
 }
+
+pub(crate) fn get_features() -> Vec<String> {
+    let mut r = Vec::new();
+    #[cfg(feature = "fedora-integration")]
+    r.push("fedora-integration".to_string());
+    r
+}

src/app/libmain.cxx

@@ -32,6 +32,7 @@
 
 #include "rpmostree-util.h"
 #include "rpmostree-builtins.h"
+#include "rpmostree-cxxrs.h"
 #include "rpmostree-polkit-agent.h"
 #include "rpmostreemain.h"
 
@@ -248,6 +249,11 @@ rpmostree_option_context_parse (GOptionContext *context,
       g_print (" Features:\n");
       for (char **iter = features; iter && *iter; iter++)
         g_print ("  - %s\n", *iter);
+      auto featuresrs = rpmostreecxx::get_features();
+      for (auto s : featuresrs)
+        {
+          g_print ("  - %s\n", s.c_str());
+        }
       exit (EXIT_SUCCESS);
     }