Extract footer preference as a widget lib

Currently, developer needs to import SettingsLib to use
footer preference. But the size of SettingsLib is too huge.

We extract the footer preference as a lib so that developer
only needs to import a small lib for using footer.

Test: Rebuilt apk, and see the footer preference
Fix: 173088235
Change-Id: I35ba99a49c7a13542d79f0340eecdbe9844102d0
diff --git a/packages/SettingsLib/FooterPreference/Android.bp b/packages/SettingsLib/FooterPreference/Android.bp
new file mode 100644
index 0000000..30d9bd2
--- /dev/null
+++ b/packages/SettingsLib/FooterPreference/Android.bp
@@ -0,0 +1,13 @@
+android_library {
+    name: "SettingsLibFooterPreference",
+
+    srcs: ["src/**/*.java"],
+    resource_dirs: ["res"],
+
+    static_libs: [
+        "androidx.annotation_annotation",
+        "androidx.preference_preference",
+    ],
+    sdk_version: "system_current",
+    min_sdk_version: "21",
+}