reproducible: Fix race with externalsrc/devtool over lockfile

We occasionally see races over the lockfile used by externalsrc/devtool
when walking files for the source_date_epock calculation. Skip this file
if present to avoid the issues and fix a real issue where SDE could be
contaminated too.

[YOCTO #14921]

(From OE-Core rev: 4bc0eb4bd90e6e6e46581a8ed367212bdd910a26)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oe/reproducible.py

@@ -131,6 +131,9 @@ def get_source_date_epoch_from_youngest_file(d, sourcedir):
         files = [f for f in files if not f[0] == '.']
 
         for fname in files:
+            if fname == "singletask.lock":
+                 # Ignore externalsrc/devtool lockfile [YOCTO #14921]
+                 continue
             filename = os.path.join(root, fname)
             try:
                 mtime = int(os.lstat(filename).st_mtime)