Add prebuilts clang darwin-x86 host 3.5

This prebuilt is required to fix emulator mac build.
diff --git a/default.xml b/default.xml
index ddb1569..e707ef7 100644
--- a/default.xml
+++ b/default.xml
@@ -18,6 +18,7 @@
   <project name="platform/external/emma" path="external/emma" />
   <project name="platform/external/qemu" path="external/qemu" />
   <project name="platform/prebuilts/android-emulator" path="prebuilts/android-emulator" />
+  <project name="platform/prebuilts/clang/darwin-x86/host/3.5" path="prebuilts/clang/darwin-x86/host/3.5" />
   <project name="platform/prebuilts/eclipse-build-deps" path="prebuilts/eclipse-build-deps" />
   <project name="platform/prebuilts/eclipse-build-deps-sources" path="prebuilts/eclipse-build-deps-sources" />
   <project name="platform/prebuilts/eclipse" path="prebuilts/eclipse" />
@@ -41,4 +42,4 @@
   <project name="platform/tools/studio/google/play" path="tools/studio/google/play" />
   <project name="platform/tools/swt" path="tools/swt" />
 
-</manifest>
\ No newline at end of file
+</manifest>