Check out Hafnium without submodules

Checks out individual Hafnium repositories as Repo projects instead of
being Git submodules. The root project is checked out under `core/` and
its subfolders and important files symlinked into the root.

This way it is possible to clone and build Hafnium only with small
modifications (scripts must not do `realpath` due to symlinks). It is
meant as a first step towards migrating to Repo.

Change-Id: I5284e48f3180fb9077892b01578ac7eb0768c234
diff --git a/default.xml b/default.xml
index e068538..3937000 100644
--- a/default.xml
+++ b/default.xml
@@ -1,9 +1,38 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <manifest>
   <remote
-    name="hafnium"
+    name="origin"
     fetch="https://hafnium.googlesource.com/"
-    review="sso://hafnium.googlesource.com/"
-    revision="master" />
-  <project path="." name="hafnium" sync-s="true" remote="hafnium" />
+    review="sso://hafnium.googlesource.com/" />
+  <default remote="origin" revision="master" />
+
+  <project path="core" name="hafnium">
+    <!-- Required in the root by the build system -->
+    <linkfile src=".clang-format" dest=".clang-format" />
+    <linkfile src=".clang-tidy" dest=".clang-tidy" />
+    <linkfile src=".gn" dest=".gn" />
+    <linkfile src="BUILD.gn" dest="BUILD.gn" />
+    <linkfile src="Makefile" dest="Makefile" />
+
+    <!-- TODO: Do we want these in the root or change paths? -->
+    <linkfile src="build" dest="build" />
+    <linkfile src="kokoro" dest="kokoro" />
+    <linkfile src="inc" dest="inc" />
+    <linkfile src="src" dest="src" />
+    <linkfile src="test" dest="test" />
+    <linkfile src="vmlib" dest="vmlib" />
+
+    <!-- TODO: Move these inside the respective folders -->
+    <linkfile src="driver/BUILD.gn" dest="driver/BUILD.gn" />
+    <linkfile src="third_party/BUILD.gn" dest="third_party/BUILD.gn" />
+  </project>
+
+  <!-- Shallow clones of third-party code. -->
+  <project path="prebuilts" name="hafnium/prebuilts" clone-depth="1" />
+  <project path="third_party/googletest" name="hafnium/third_party/googletest" clone-depth="1" />
+  <project path="third_party/linux" name="hafnium/third_party/linux" clone-depth="1" />
+
+  <project path="driver/linux" name="hafnium/driver/linux" />
+  <project path="project/reference" name="hafnium/project/reference" />
+
 </manifest>