Introduce a DT-based manifest

These are first steps towards a new manifest format. A new "device_tree"
build target is introduced to compile DTS files to DTB, and
`generate_initrd.py` now does not produce a "vms.txt" file. Instead
"initrd" targets are expected to provide a path to a DTS manifest in the
format:

    /dts-v1/;

    / {
      hypervisor {
        vm1 {
	  debug_name = "primary";
	};

	vm2 {
	  debug_name = "secondary1";
	  kernel_filename = "filename";
	  vcpu_count = <N>;
          mem_size = <M>;
	};

	...
      };
    };

The information provided in the manifest matches "vms.txt".

Bug: 117551352
Test: manifest_test.cc
Test: used by hftest
Change-Id: I6b70bd44d2b110c4f7a6b971018c834084b6d8c4
diff --git a/test/linux/BUILD.gn b/test/linux/BUILD.gn
index 84e72bc..fcc5907 100644
--- a/test/linux/BUILD.gn
+++ b/test/linux/BUILD.gn
@@ -57,11 +57,10 @@
 initrd("linux_test") {
   testonly = true
 
+  manifest = "manifest.dts"
   primary_vm = "//third_party:linux__prebuilt"
   primary_initrd = ":linux_test_initrd"
   secondary_vms = [ [
-        "1048576",
-        "1",
         "socket0",
         ":socket_vm0",
       ] ]
diff --git a/test/linux/manifest.dts b/test/linux/manifest.dts
new file mode 100644
index 0000000..5437968
--- /dev/null
+++ b/test/linux/manifest.dts
@@ -0,0 +1,32 @@
+/*
+ * Copyright 2019 The Hafnium Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/dts-v1/;
+
+/ {
+	hypervisor {
+		vm1 {
+			debug_name = "primary";
+		};
+
+		vm2 {
+			debug_name = "socket0";
+			vcpu_count = <1>;
+			mem_size = <0x100000>;
+			kernel_filename = "socket0";
+		};
+	};
+};