deb: build the tree the caller pointed at before the name search

build_binary_package stages the parent of the requested cwd, then
re-derived the package directory inside the staging area from
package/version name patterns plus the calling process's working
directory. That only works by accident for interactive users sitting
in the package directory: an embedded caller whose tree lives at
<job>/tree matches no pattern, and the process cwd means nothing to
a library consumer — the bc build above failed here even though the
tree was staged correctly.

The pointed-at tree is authoritative anyway: its changelog defined
the package, version and series for this build. Resolve its staged
copy outright when it carries a debian/ tree, keep the pattern
search (with the quirks overrides) as a fallback, and hand the
resolved directory to local::build instead of searching again.

src/deb/local.rs

@@ -34,6 +34,7 @@ pub async fn build(
     series: &str,
     pocket: Option<&str>,
     build_root: &str,
+    package_dir: &Path,
     cross: bool,
     ppa: &[String],
     inject_packages: &[String],
@@ -231,10 +232,8 @@ pub async fn build(
         return Err("Could not install essential packages for the build".into());
     }
 
-    // Find the actual package directory
-    // Find the actual package directory
-    let package_dir =
-        crate::deb::find_package_directory(Path::new(build_root), package, version, series, &ctx)?;
+    // The package directory was resolved by the caller (the staged copy of
+    // the tree the user pointed at, or the name-pattern search fallback)
     let package_dir_str = package_dir
         .to_str()
         .ok_or("Invalid package directory path")?;