Integration test for updatable system font.

This test:
(1) signs a font file with the test key.
(2) side-loads the test cert to the device under test.
(3) verifies that the signed font file can be installed.

The device must be rootable for doing step (2).

Bug: 176939176
Test: atest UpdatableSystemFontTest
Change-Id: I7a9b614aa3c77589c3495b663cb76056ba657006

Android.bp

@@ -1294,6 +1294,18 @@ python_binary_host {
     ],
 }
 
+python_binary_host {
+    name: "update_font_metadata",
+    defaults: ["base_default"],
+    main: "tools/fonts/update_font_metadata.py",
+    srcs: [
+        "tools/fonts/update_font_metadata.py",
+    ],
+    libs: [
+        "fontTools",
+    ],
+}
+
 filegroup {
     name: "framework-media-annotation-srcs",
     srcs: [