manifest: use forked art

Change-Id: I4d6f5e9dfee4ed3714d1e40fd93b0d17c9ac5590
diff --git a/omni-aosp.xml b/omni-aosp.xml
index be6ec06..d144188 100644
--- a/omni-aosp.xml
+++ b/omni-aosp.xml
@@ -8,6 +8,7 @@
            fetch="https://github.com/omnirom"
            review="gerrit.omnirom.org" />
 
+  <project path="art" name="android_art" remote="omnirom" revision="android-8.1" groups="pdk" />
   <project path="bionic" name="android_bionic" remote="omnirom" revision="android-8.1" groups="pdk" />
 
   <project path="build/make" name="android_build" remote="omnirom" revision="android-8.1" groups="pdk" >