Allow minijail to be built as an Android Rust library

Recent changes in crosvm:

https://chromium.googlesource.com/chromiumos/platform/crosvm/+/a2d845a569494a3924e587b7d63487832cf55ab8

use minijail as a separate dependency.

This allows us to use the current minijail in AOSP to build crosvm
in the Android source tree.

Change-Id: I15cc9b3e408deec1b34ff387a2c27fd3ac1cd243
diff --git a/Android.bp b/Android.bp
index 2555c44..687a366 100644
--- a/Android.bp
+++ b/Android.bp
@@ -414,3 +414,20 @@
     static_libs: ["libminijail_generated"],
     shared_libs: minijailCommonLibraries + ["libminijail"],
 }
+
+// Generated by cargo2android.
+rust_library_host_rlib {
+    name: "libminijail_sys",
+    crate_name: "minijail_sys",
+    srcs: ["lib.rs"],
+    edition: "2018",
+    rlibs: [
+        "liblibc",
+    ],
+    static_libs: [
+        "libminijail",
+    ],
+    shared_libs: [
+        "libcap",
+    ],
+}