multidex: Update path to android.jar.

This file has been copied to a new location. Update the multidex gradle
build to refer the new location so that the old one can be deleted.

Test: No
Bug: 77525052
Change-Id: Ic7a1c19be543a06d01ad0b48b909c4e116327e5e
diff --git a/build.gradle b/build.gradle
index b9af213..6665846 100644
--- a/build.gradle
+++ b/build.gradle
@@ -42,7 +42,7 @@
 } else {
     gradle.ext.currentSdk = 'current'
     ext.buildToolsVersion = '26.0.0'
-    project.ext.androidJar = files("${project.rootDir}/../../prebuilts/sdk/current/android.jar")
+    project.ext.androidJar = files("${project.rootDir}/../../prebuilts/sdk/current/public/android.jar")
     File props = file("local.properties")
     props.write "android.dir=../../"
 }