Add a utility function for writing depfiles.

Change-Id: Ic365e3e1632d518a5331646ed5deef1b5a36f2f6
diff --git a/Blueprints b/Blueprints
index 80c27d0..ae9aa95 100644
--- a/Blueprints
+++ b/Blueprints
@@ -23,6 +23,12 @@
 }
 
 bootstrap_go_package {
+    name:    "blueprint-deptools",
+    pkgPath: "blueprint/deptools",
+    srcs:    ["blueprint/deptools/depfile.go"],
+}
+
+bootstrap_go_package {
     name:    "blueprint-pathtools",
     pkgPath: "blueprint/pathtools",
     srcs:    ["blueprint/pathtools/lists.go"],
@@ -37,6 +43,7 @@
 bootstrap_go_package {
     name:    "blueprint-bootstrap",
     deps:    ["blueprint",
+              "blueprint-deptools",
               "blueprint-pathtools"],
     pkgPath: "blueprint/bootstrap",
     srcs:    ["blueprint/bootstrap/bootstrap.go",
@@ -49,4 +56,4 @@
     name: "minibp",
     deps: ["blueprint", "blueprint-bootstrap"],
     srcs: ["blueprint/bootstrap/minibp/main.go"],
-}
\ No newline at end of file
+}