Add MicrodroidHostTestCases

The test is to enture that the boot flow explained in
microdroid/README.md is not broken.

Bug: 181860941
Test: atest MicrodroidHostTestCases

Change-Id: Ic084ed2fe82f971092f28de776182e77ee360350
diff --git a/microdroid/Android.bp b/microdroid/Android.bp
index 488765f..945a27a 100644
--- a/microdroid/Android.bp
+++ b/microdroid/Android.bp
@@ -141,15 +141,15 @@
 bootimg {
     name: "microdroid_boot-5.10",
     ramdisk_module: "microdroid_ramdisk-5.10",
-    enabled: false,
+    // We don't have kernel for arm and x86. But Soong demands one when it builds for
+    // arm or x86 target. Satisfy that by providing an empty file as the kernel.
+    kernel_prebuilt: "empty_kernel",
     arch: {
         arm64: {
             kernel_prebuilt: ":kernel_prebuilts-5.10-arm64",
-            enabled: true,
         },
         x86_64: {
             kernel_prebuilt: ":kernel_prebuilts-5.10-x86_64",
-            enabled: true,
         },
     },
     // TODO(jiyong): change the name to init, cause it's confusing
@@ -192,15 +192,6 @@
     header_version: "4",
     vendor_boot: true,
     partition_name: "vendor_boot",
-    enabled: false,
-    arch: {
-        arm64: {
-            enabled: true,
-        },
-        x86_64: {
-            enabled: true,
-        },
-    },
 }
 
 android_filesystem {