Stamp nightly builds with commit-based runtime version

build.rs

@@ -4,6 +4,14 @@ use std::path::Path;
 
 fn main() {
     println!("cargo:rerun-if-changed=web/dist");
+    println!("cargo:rerun-if-env-changed=ALCHEMIST_VERSION");
+
+    if let Some(version) = env::var_os("ALCHEMIST_VERSION") {
+        println!(
+            "cargo:rustc-env=ALCHEMIST_BUILD_VERSION={}",
+            version.to_string_lossy()
+        );
+    }
 
     if env::var_os("CARGO_FEATURE_EMBED_WEB").is_none() {
         return;