veyron/examples/{mdb,todos}: look for built binaries under $REPO_ROOT, not $VEYRON_ROOT

Change-Id: I5e84781395d5f24a582e89fc21b26fe459de8789
diff --git a/examples/mdb/run.sh b/examples/mdb/run.sh
index 4265ec2..32fca4f 100755
--- a/examples/mdb/run.sh
+++ b/examples/mdb/run.sh
@@ -21,7 +21,7 @@
     VIEWER_PORT_FILE="$1"
   fi
   local -r VIEWER_PORT_FILE
-  local -r VEYRON_BIN="${VEYRON_ROOT}/veyron/go/bin"
+  local -r VEYRON_BIN="${REPO_ROOT}/go/bin"
 
   # Generate a self-signed identity.
   "${VEYRON_BIN}/identity" generate > "${ID_FILE}"
diff --git a/examples/todos/run.sh b/examples/todos/run.sh
index eb2cd0e..fbda5df 100755
--- a/examples/todos/run.sh
+++ b/examples/todos/run.sh
@@ -21,7 +21,7 @@
     VIEWER_PORT_FILE="$1"
   fi
   local -r VIEWER_PORT_FILE
-  local -r VEYRON_BIN="${VEYRON_ROOT}/veyron/go/bin"
+  local -r VEYRON_BIN="${REPO_ROOT}/go/bin"
 
   # Generate a self-signed identity.
   "${VEYRON_BIN}/identity" generate > "${ID_FILE}"