Add generic Android target to test Android boot flow

Android boot flow is currently not being built in the reference project.
This means it does not get built in presubmit/continuous builds either.
Add a dummy Android target to remedy that.

Change-Id: Iba6cc9d877249ac0b149cf12bbc3fbc4d11494da
diff --git a/BUILD.gn b/BUILD.gn
index f4c684a..4a5acf0 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -18,6 +18,7 @@
 group("root") {
   deps = [
     "//src:hafnium(:aem_v8a_fvp_clang)",
+    "//src:hafnium(:android_aarch64_clang)",
     "//src:hafnium(:qemu_aarch64_clang)",
     "//src:hafnium(:rpi4_clang)",
   ]
@@ -101,3 +102,20 @@
     core_freq_mhz = 500
   }
 }
+
+# Generic target which uses the Android boot flow. It is not intended to run on
+# any Android platform. It exists only to test building Android-specific code.
+aarch64_toolchains("android_aarch64") {
+  cpu = "cortex-a57"
+  origin_address = "0x0"
+  boot_flow = "//src/boot_flow:android"
+  console = "//src/arch/aarch64/pl011"
+  iommu = "//src/iommu:absent"
+  gic_version = 2
+  heap_pages = 60
+  max_cpus = 8
+  max_vms = 16
+  toolchain_args = {
+    pl011_base_address = "0x09000000"
+  }
+}