something obvious is wrong..

libcsp-cargo-build/Cargo.toml

@@ -3,6 +3,7 @@ name = "libcsp-cargo-build"
 version = "0.1.0"
 edition = "2021"
 
+[lib]
+
 [dependencies]
 cc = "1"
-walkdir = "2"

libcsp-cargo-build/src/lib.rs

@@ -23,13 +23,19 @@ pub struct Builder {
     build: cc::Build,
 }
 
-impl Builder {
-    pub fn new() -> Self {
+impl Default for Builder {
+    fn default() -> Self {
         Self {
             opts: CspBuildOpts::default(),
             build: cc::Build::new(),
         }
     }
+}
+
+impl Builder {
+    pub fn new() -> Self {
+        Self::default()
+    }
 
     pub fn cc(&mut self) -> &mut cc::Build {
         &mut self.build
@@ -77,6 +83,7 @@ impl Builder {
 
         self.build.compile("csp");
     }
+
     #[cfg(unix)]
     fn posix_arch_files(&mut self) {
         self.build