Use fs-verity digests proto to build the directory

The proto contains path -> digest mapping. In this change, we start to
use the provided protobuf to build the directory. Digest is not yet
used.

Bug: 206869687
Test: atest AuthFsHostTest ComposHostTestCases MicrodroidTestCase
Change-Id: I0f03219c1243f20f9ec5099a451c6f588add9608
diff --git a/compos/src/compilation.rs b/compos/src/compilation.rs
index 4837029..9a23bf5 100644
--- a/compos/src/compilation.rs
+++ b/compos/src/compilation.rs
@@ -122,9 +122,9 @@
         port: FD_SERVER_PORT,
         inputDirFdAnnotations: vec![InputDirFdAnnotation {
             fd: context.system_dir_fd,
-            // TODO(206869687): Replace /dev/null with the real path when possible.
-            manifestPath: "/dev/null".to_string(),
-            prefix: "/system".to_string(),
+            // 0 is the index of extra_apks in vm_config_extra_apk.json
+            manifestPath: "/mnt/extra-apk/0/assets/build_manifest.pb".to_string(),
+            prefix: "system/".to_string(),
         }],
         outputDirFdAnnotations: vec![
             OutputDirFdAnnotation { fd: context.output_dir_fd },
diff --git a/compos/tests/java/android/compos/test/ComposKeyTestCase.java b/compos/tests/java/android/compos/test/ComposKeyTestCase.java
index d7c0058..d59d3d9 100644
--- a/compos/tests/java/android/compos/test/ComposKeyTestCase.java
+++ b/compos/tests/java/android/compos/test/ComposKeyTestCase.java
@@ -41,9 +41,12 @@
     /** Wait time for service to be ready on boot */
     private static final int READY_LATENCY_MS = 10 * 1000; // 10 seconds
 
-    // Path to compos_key_cmd tool
+    /** Path to compos_key_cmd tool */
     private static final String COMPOS_KEY_CMD_BIN = "/apex/com.android.compos/bin/compos_key_cmd";
 
+    /** Config of the test VM. This is a path inside the APK. */
+    private static final String VM_TEST_CONFIG_PATH = "assets/vm_test_config.json";
+
     private String mCid;
 
     @Before
@@ -132,7 +135,7 @@
                         getBuild(),
                         /* apkName, no need to install */ null,
                         packageName,
-                        "assets/vm_test_config.json",
+                        VM_TEST_CONFIG_PATH,
                         /* debug */ true,
                         /* use default memoryMib */ 0,
                         Optional.empty(),