added 1.3.0-alpha1 to prebuits.

Change-Id: Ia39b6a9d82122c1ac1ebc9fb32c411da08ff8190
diff --git a/com/android/tools/layoutlib/layoutlib-api/24.3.0-alpha1/layoutlib-api-24.3.0-alpha1.jar.sha1 b/com/android/tools/layoutlib/layoutlib-api/24.3.0-alpha1/layoutlib-api-24.3.0-alpha1.jar.sha1
new file mode 100644
index 0000000..f13a7c7
--- /dev/null
+++ b/com/android/tools/layoutlib/layoutlib-api/24.3.0-alpha1/layoutlib-api-24.3.0-alpha1.jar.sha1
@@ -0,0 +1 @@
+8b36a59c80e1663145078b0cdc7075793937682a
\ No newline at end of file