Microdroid stores APEX pubkeys in instance.img

Just like APK's root hash, APEX pubkeys are stored in instance.img so
that in subsequent boots, pubkeys from payload APEXes are checked
against ones in instance.img.

Bug: 198361718
Test: MicrodroidHostTestCases
Change-Id: I5385700e86b4962133df80b750208ce45cec2655
diff --git a/microdroid_manager/Android.bp b/microdroid_manager/Android.bp
index 104c04a..9957689 100644
--- a/microdroid_manager/Android.bp
+++ b/microdroid_manager/Android.bp
@@ -32,6 +32,7 @@
         "libuuid",
         "libvsock",
         "librand",
+        "libzip",
     ],
     shared_libs: [
         "libbinder_rpc_unstable",