Codegen Android: fixed CI due to bad SRC->OUT dir copy

Summary:
The recursive copy statement fixed here behaved differently in MacOS vs Linus (CI), because of the missing dot (.)

The trailing slash on the source directory behaves differently on Mac (BSD) than Linux (GNU):

> If the source_file ends in a /, the contents of the directory are copied rather than the directory itself.

This should fix the CI failure: https://app.circleci.com/pipelines/github/facebook/react-native/6847/workflows/36d59aab-bc4a-4d21-9ce1-a8348e71aea3/jobs/173681

Changelog: [Internal]

Reviewed By: RSNara

Differential Revision: D24560543

fbshipit-source-id: c3ab2c28616b717891bcf5d2ad762340cfb97e3d

Author: fkgozali

packages/react-native-codegen/DEFS.bzl

@@ -77,7 +77,7 @@ def rn_codegen_cli():
             bash = r"""
                 set -euo pipefail
                 mkdir -p "$OUT"
-                cp -r "$SRCDIR/" "$OUT/"
+                cp -r "$SRCDIR/." "$OUT/"
                 cd "$OUT"
                 yarn install 2> >(grep -v '^warning' 1>&2)
                 yarn run build