If we don't have feature = "toml" set, don't run rust-skeptic

build.rs

@@ -1,5 +1,20 @@
+#[cfg(feature = "toml")]
 extern crate skeptic;
 
+#[cfg(feature = "toml")]
 fn main() {
     skeptic::generate_doc_tests(&["README.md"]);
 }
+
+#[cfg(not(feature = "toml"))]
+fn main() {
+    // tests/skeptic.rs still expects a file to be at OUT_DIR/skeptic-tests.rs, so
+    // make a dummy one
+    use std::{env, fs::OpenOptions, path::Path};
+    let out_dir = Path::new(&env::var("OUT_DIR").expect("no out_dir set")).join("skeptic-tests.rs");
+    let f = OpenOptions::new()
+        .create(true)
+        .write(true)
+        .open(out_dir)
+        .expect("couldn't write to file");
+}