diff --git a/cutekit/builder.py b/cutekit/builder.py
index a21c01f..464ad69 100644
--- a/cutekit/builder.py
+++ b/cutekit/builder.py
@@ -203,8 +203,10 @@ def build(
     all = False
     shell.mkdir(target.builddir)
     ninjaPath = os.path.join(target.builddir, "build.ninja")
-    with open(ninjaPath, "w") as f:
-        gen(f, target, registry)
+
+    if not os.path.exists(ninjaPath):
+        with open(ninjaPath, "w") as f:
+            gen(f, target, registry)
 
     if components is None:
         all = True
@@ -228,10 +230,9 @@ def build(
         )
 
     outs = list(map(lambda p: str(p.path), products))
-    if all:
-        shell.exec("ninja", "-f", ninjaPath)
-    else:
-        shell.exec("ninja", "-f", ninjaPath, *outs)
+
+    shell.exec("ninja", "-f", ninjaPath, *(outs if not all else []))
+
     return products
 
 
diff --git a/cutekit/model.py b/cutekit/model.py
index 6cd5a3f..63647dd 100644
--- a/cutekit/model.py
+++ b/cutekit/model.py
@@ -71,7 +71,7 @@ class Manifest(DataClassJsonMixin):
         """
         Return the directory of the manifest
         """
-        return os.path.dirname(self.path)
+        return os.path.relpath(os.path.dirname(self.path), Path.cwd())
 
     def subpath(self, path) -> Path:
         return Path(self.dirname()) / path
@@ -121,19 +121,18 @@ class Project(Manifest):
 
     @staticmethod
     def ensure() -> "Project":
+        """
+        Ensure that a project exists in the current directory or any parent directory
+        and chdir to the root of the project.
+        """
         project = Project.topmost()
         if project is None:
             raise RuntimeError(
                 "No project found in this directory or any parent directory"
             )
+        os.chdir(project.dirname())
         return project
 
-    def chdir(self):
-        """
-        Change the current working directory to the root of the project
-        """
-        os.chdir(self.dirname())
-
     @staticmethod
     def at(path: Path) -> Optional["Project"]:
         projectManifest = Manifest.tryLoad(path / "project")