Refactor and enhance source management and installation processes

- Improved error handling and context messages in `checkout` function in `git.rs`.
- Updated license field in package specification to use a vector in `hooks.rs`.
- Enhanced `copy_manual_sources` function in `mod.rs` to support both local file and remote URL sources, including checksum verification.
- Added new utility functions for path normalization and skipping installation of specific files in `staging/mod.rs`.
- Implemented logic to handle existing files during installation, allowing for `.depotnew` suffix for kept files.
- Added tests for manual source copying, installation behavior, and path validation.
- Introduced a new LICENSE file with MIT License terms.

src/cross.rs

@@ -203,12 +203,16 @@ endian = 'little'
     }
 }
 
-/// Find a cross-compilation tool in PATH
+/// Find a cross-compilation tool in PATH and return its absolute path
 fn find_tool(prefix: &str, suffixes: &[&str], required: bool) -> Result<String> {
     for suffix in suffixes {
         let tool_name = format!("{}-{}", prefix, suffix);
-        if tool_exists(&tool_name) {
-            return Ok(tool_name);
+        // Use `which` to resolve to an absolute path (so callers get a usable path)
+        if let Ok(output) = Command::new("which").arg(&tool_name).output() {
+            if output.status.success() {
+                let path = String::from_utf8_lossy(&output.stdout).trim().to_string();
+                return Ok(path);
+            }
         }
     }
 
@@ -222,12 +226,3 @@ fn find_tool(prefix: &str, suffixes: &[&str], required: bool) -> Result<String>
 
     Err(anyhow::anyhow!("Tool not found"))
 }
-
-/// Check if a tool exists in PATH
-fn tool_exists(name: &str) -> bool {
-    Command::new("which")
-        .arg(name)
-        .output()
-        .map(|o| o.status.success())
-        .unwrap_or(false)
-}