added 1.3.0-alpha4 to prebuilts.

Change-Id: I0017ef8c05cfe7449d7b78ab09d81cbc0fa6331f
diff --git a/com/android/tools/build/builder/1.3.0-alpha4/builder-1.3.0-alpha4-sources.jar.md5 b/com/android/tools/build/builder/1.3.0-alpha4/builder-1.3.0-alpha4-sources.jar.md5
new file mode 100644
index 0000000..ba09a44
--- /dev/null
+++ b/com/android/tools/build/builder/1.3.0-alpha4/builder-1.3.0-alpha4-sources.jar.md5
@@ -0,0 +1 @@
+25017741469455b701a9a0fee9ade37c
\ No newline at end of file