galaxy build - ignore existing MANIFEST and FILES (#76479) (#76498)

(cherry picked from commit 8482ee4e9a)

changelogs/fragments/galaxy-build-files-ignore.yml

@@ -0,0 +1,4 @@
+bugfixes:
+- >-
+  ansible-galaxy collection build - Ignore any existing ``MANIFEST.json`` and ``FILES.json`` in the root directory
+  when building a collection.

lib/ansible/galaxy/collection.py

@@ -931,6 +931,8 @@ def _build_files_manifest(b_collection_path, namespace, name, ignore_patterns):
     # We always ignore .pyc and .retry files as well as some well known version control directories. The ignore
     # patterns can be extended by the build_ignore key in galaxy.yml
     b_ignore_patterns = [
+        b'MANIFEST.json',
+        b'FILES.json',
         b'galaxy.yml',
         b'galaxy.yaml',
         b'.git',