Build libghostty-vt separately so Gentoo Zig flags and offline inputs apply.
Avoid initializing unused Ghostty GUI build steps in lib-vt mode.
Applies to Herdr 0.9.3.

--- a/crates/ghostty-vt/build.rs
+++ b/crates/ghostty-vt/build.rs
@@ -32,6 +32,12 @@ fn env_bool(name: &str) -> Option<bool> {
 }
 
 fn main() {
+    if let Ok(lib_dir) = env::var("LIBGHOSTTY_VT_LIB_DIR") {
+        println!("cargo:rerun-if-env-changed=LIBGHOSTTY_VT_LIB_DIR");
+        println!("cargo:rustc-link-search=native={lib_dir}");
+        println!("cargo:rustc-link-lib=static=ghostty-vt");
+        return;
+    }
     // The vendored source stays at the repository root, shared with its maintenance scripts.
     let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR"));
     let vendor_dir = manifest_dir.join("../../vendor");
--- a/vendor/libghostty-vt/build.zig
+++ b/vendor/libghostty-vt/build.zig
@@ -57,6 +57,15 @@ pub fn build(b: *std.Build) !void {
         &deps,
     );
 
+    if (config.emit_lib_vt) {
+        const lib = try buildpkg.GhosttyLibVt.initStatic(b, &mod);
+        b.getInstallStep().dependOn(&b.addInstallLibFile(
+            lib.output,
+            "libghostty-vt.a",
+        ).step);
+        return;
+    }
+
     // All our steps which we'll hook up later. The steps are shown
     // up here just so that they are more self-documenting.
     const run_step = b.step("run", "Run the app");