Revert TARGET_BUILD_UNBUNDLED for buildbot builds.

It interferes with building on a full platform tree. This partially
reverts https://r.android.com/1324611.

Test: art/tools/buildbot-build.sh on AOSP master
Bug: 157549171
Change-Id: Ie56ecd4c6df9d134f1ce11f32f0940390de6ada3
diff --git a/tools/buildbot-build.sh b/tools/buildbot-build.sh
index fd6c6ca..dde156d 100755
--- a/tools/buildbot-build.sh
+++ b/tools/buildbot-build.sh
@@ -63,7 +63,7 @@
 done
 
 # Allow to build successfully in master-art.
-extra_args="SOONG_ALLOW_MISSING_DEPENDENCIES=true TARGET_BUILD_UNBUNDLED=true"
+extra_args="SOONG_ALLOW_MISSING_DEPENDENCIES=true"
 
 apexes=(
   "com.android.art.testing"