Add `ld.config.txt` file to Android Runtime APEX packages.

This file is required when the Runtime APEX directories are part of
Bionic search paths.

The `ld.config.txt` file added by this change is currently empty.
Follow-up commits will add actual content to it.

Test: Device boot test with Android Runtime APEX.
Test: Device boot test without Android Runtime APEX.
Test: cts-tradefed run cts --m vm-tests-tf
Bug: 113373927
Bug: 119949783
Change-Id: I3df75b1460a43b410663ad816b5e01b9846b3fcb
diff --git a/build/apex/Android.bp b/build/apex/Android.bp
index 159e5c1..f1a21e8 100644
--- a/build/apex/Android.bp
+++ b/build/apex/Android.bp
@@ -72,6 +72,13 @@
     private_key: "com.android.runtime.pem",
 }
 
+prebuilt_etc {
+    name: "com.android.runtime.ld.config.txt",
+    src: "ld.config.txt",
+    filename: "ld.config.txt",
+    installable: false,
+}
+
 // TODO: Introduce `apex_defaults` to factor common parts of `apex`
 // module definitions below?
 
@@ -97,9 +104,8 @@
             binaries: [],
         }
     },
+    prebuilts: ["com.android.runtime.ld.config.txt"],
     key: "com.android.runtime.key",
-    // TODO: Also package a `ld.config.txt` config file (to be placed in `etc/`).
-    // ...
 }
 
 // "Debug" version of the Runtime APEX module (containing both release and
@@ -126,7 +132,6 @@
             binaries: art_tools_binaries,
         }
     },
+    prebuilts: ["com.android.runtime.ld.config.txt"],
     key: "com.android.runtime.key",
-    // TODO: Also package a `ld.config.txt` config file (to be placed in `etc/`).
-    // ...
 }