Added:

- `build.kind = "efi"` — UEFI PE32+ executable support. Links with `-shared -nostdlib -Wl,-dll -Wl,--subsystem,10`, output via `efi_path()` with `.efi` extension, rejected by `dcr run`.
- `build.kind = "elf"` — bare-metal ELF executable support. Uses `elf_path()` output path, rejected by `dcr run`, no extra linker flags.

Fixed:

- `dcr run` with `--target` or `build.target` now correctly finds the binary in the arch-specific target directory.
- `dcr run` checks profile-specific `build.{profile}.kind` before rejecting library builds (previously only checked `build.kind`).
- `dcr clean` now reads `build.target` from `dcr.toml` when no `--target` flag is given.
- Linux: target directory is now consistent — `target/<arch>-unknown-linux-gnu/<profile>/` (no stale `target/<profile>/`).
- `dcr.lock` is now populated with all resolved dependencies (registry, path, git) instead of being always empty.
- Git dependencies are now properly recognized and recorded in `dcr.lock`.
- `is_registry_dep` correctly identifies version-based registry dependency tables (`{ version = "..." }`) and rejects tables with unknown keys.
- `dcr test` accepts `--debug`/`--release` flags (defaults to `debug` profile instead of always `release`).
- Build fingerprint cache (`build_cache_path`) now includes `target_dir` — different targets no longer share a single cache entry.
- `object_path` no longer hardcodes the `src/` prefix — works correctly with custom `build.roots` (e.g. `roots = ["lib"]`).
- `dcr update` now generates `.exe` candidates for all Windows targets, not just `x86_64-pc-windows-msvc`.
- Compiler existence is verified before starting the build (clear error if compiler is not found in PATH).
- Consolidated duplicate `OUTPUT_MUTEX` definitions — MSVC backend now uses the shared mutex from `common.rs`.
- Registry cache root directory is created if missing (prevents cryptic errors when `~/.dcr/` does not exist).

src/core/builder/common.rs

@@ -5,6 +5,10 @@ use std::sync::{Mutex, OnceLock};
 
 static OUTPUT_MUTEX: OnceLock<Mutex<()>> = OnceLock::new();
 
+pub fn get_output_lock() -> &'static Mutex<()> {
+    OUTPUT_MUTEX.get_or_init(|| Mutex::new(()))
+}
+
 pub fn collect_sources(
     roots: &[PathBuf],
     extensions: &[&str],
@@ -230,10 +234,16 @@ pub fn normalize_source_path(path: &Path) -> String {
 
 pub fn object_path(obj_dir: &Path, source: &str, obj_ext: &str) -> String {
     let src_path = Path::new(source);
-    let rel = src_path
-        .strip_prefix("./src")
-        .or_else(|_| src_path.strip_prefix("src"))
-        .unwrap_or(src_path);
+    let stripped = src_path.strip_prefix("./").unwrap_or(src_path);
+    let rel = stripped
+        .components()
+        .skip(1)
+        .collect::<std::path::PathBuf>();
+    let rel = if rel.components().next().is_some() {
+        rel
+    } else {
+        stripped.to_path_buf()
+    };
     let mut out = obj_dir.join(rel);
     out.set_extension(obj_ext.trim_start_matches('.'));
     out.to_string_lossy().to_string()