Allow to build the update.zip for emulator build.

img_from_target_files.py just skipps the boot.img and recovery.img since
there is no kernel or recovery.fstab for emulator.

Bug: 15383279
Change-Id: I4035193e6ab933194ff1417dfae4eab963fe5301
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index fea335e..efba1fe 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -498,6 +498,8 @@
   if target.endswith(".img"): target = target[:-4]
   mount_point = "/" + target
 
+  fs_type = None
+  limit = None
   if info_dict["fstab"]:
     if mount_point == "/userdata": mount_point = "/data"
     p = info_dict["fstab"][mount_point]
diff --git a/tools/releasetools/img_from_target_files.py b/tools/releasetools/img_from_target_files.py
index 93092b3..6be5a52 100755
--- a/tools/releasetools/img_from_target_files.py
+++ b/tools/releasetools/img_from_target_files.py
@@ -269,11 +269,14 @@
 
   output_zip = zipfile.ZipFile(args[1], "w", compression=zipfile.ZIP_DEFLATED)
 
-  common.GetBootableImage(
-      "boot.img", "boot.img", OPTIONS.input_tmp, "BOOT").AddToZip(output_zip)
-  common.GetBootableImage(
-      "recovery.img", "recovery.img", OPTIONS.input_tmp,
-      "RECOVERY").AddToZip(output_zip)
+  boot_image = common.GetBootableImage(
+      "boot.img", "boot.img", OPTIONS.input_tmp, "BOOT")
+  if boot_image:
+      boot_image.AddToZip(output_zip)
+  recovery_image = common.GetBootableImage(
+      "recovery.img", "recovery.img", OPTIONS.input_tmp, "RECOVERY")
+  if recovery_image:
+    recovery_image.AddToZip(output_zip)
 
   if not bootable_only:
     AddSystem(output_zip)