feat: Implement build state tracking and interactive package specification creation

- Added StateTracker to manage build steps and allow resuming interrupted builds.
- Updated post_extract function to utilize StateTracker for patch and command execution.
- Introduced makefile.rs to handle building and installing packages via Makefile.
- Created interactive.rs for an interactive package specification creator with SHA256 computation for source URLs.
- Enhanced checksum verification to support multiple algorithms (SHA256, SHA512, MD5).
- Added example configuration files in contrib for system-wide and user-level Depot configurations.
- Updated tests to cover new functionality and ensure correctness of state tracking and interactive creation.

src/builder/rust.rs

@@ -52,6 +52,11 @@ pub fn build(
         env_vars.push(("RUSTFLAGS", flags.rustflags.join(" ")));
     }
 
+    // CARCH support
+    if !flags.carch.is_empty() {
+        env_vars.push(("CARCH", flags.carch.clone()));
+    }
+
     // If cross-compiling, set linker via CARGO_TARGET_*_LINKER
     if let Some(cc_cfg) = cross {
         // Convert target triple to uppercase with underscores for env var
@@ -71,6 +76,9 @@ pub fn build(
         env_vars.push(("RUSTUP_TOOLCHAIN", "stable".to_string()));
     }
 
+    // Export DEPOT_ROOTFS so build scripts can detect the target rootfs
+    env_vars.push(("DEPOT_ROOTFS", flags.rootfs.clone()));
+
     // Run cargo build
     println!(
         "Running cargo build ({})...",