Don't run pub in checked mode in the built SDK.

sdk/bin/pub_developer

Index: sdk/bin/pub_developer
diff --git a/sdk/bin/pub b/sdk/bin/pub_developer
similarity index 96%
copy from sdk/bin/pub
copy to sdk/bin/pub_developer
index 364308575a70b78b474370ad71ba9da071876103..be0510d990fbc78797d73fe57c7d153a5591215b 100755
--- a/sdk/bin/pub
+++ b/sdk/bin/pub_developer
@@ -17,7 +17,7 @@ SNAPSHOT="$BIN_DIR/snapshots/pub.dart.snapshot"
 if test -f "$SNAPSHOT"; then
   # We are running the snapshot in the built SDK.
   DART="$BIN_DIR/dart"
-  exec "$DART" "--checked" "$SNAPSHOT" "$@"
+  exec "$DART" --checked "$SNAPSHOT" "$@"
 else
   # We are running pub from source in the development repo.
   if [ -z "$DART_CONFIGURATION" ];