lib: constants: change CHROMITE_BIN_DIR to Path

BUG=None
TEST=CQ passes

Change-Id: Id3885f232af7a700f33183164b43d1da4295145f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4374329
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Ram Chandrasekar <rchandrasekar@google.com>
diff --git a/scripts/cros_fuzz.py b/scripts/cros_fuzz.py
index e6b3ec9..79b00d1 100644
--- a/scripts/cros_fuzz.py
+++ b/scripts/cros_fuzz.py
@@ -859,7 +859,7 @@
     """
 
     # Path to the lddtree chromite script.
-    LDDTREE_SCRIPT_PATH = os.path.join(constants.CHROMITE_BIN_DIR, "lddtree")
+    LDDTREE_SCRIPT_PATH = constants.CHROMITE_BIN_DIR / "lddtree"
 
     def __init__(self, binary):
         self.binary = binary