Add --clear to uv build to remove old build artifacts (#16371)

Add `uv build --clear` that behaves like `rm -r ./dist && uv build` to
clear artifacts from previous builds. This avoids accidentally
publishing the wrong artifacts and removes accumulated old builds.

See https://github.com/astral-sh/uv/issues/10293#issuecomment-3405904013
Fixes #10293

crates/uv-cli/src/lib.rs

@@ -2635,6 +2635,10 @@ pub struct BuildArgs {
     #[arg(long, conflicts_with = "list")]
     pub force_pep517: bool,
 
+    /// Clear the output directory before the build, removing stale artifacts.
+    #[arg(long)]
+    pub clear: bool,
+
     /// Constrain build dependencies using the given requirements files when building distributions.
     ///
     /// Constraints files are `requirements.txt`-like files that only control the _version_ of a