Add extra new line before .local_cuda.bazelrc (#1113)

Sometimes when there is no new line at the end of `.bazelrc` file, it
will end up with `try-import %workspace%/.bazelrc.usertry-import
%workspace%/.local_cuda.bazelrc`.

For example this commit did not contain a new line at the end:
jax-ml/jax@a2bc8c2

.github/container/build-jax.sh

@@ -265,7 +265,7 @@ if [[ ! -e "/usr/local/cuda/lib" ]]; then
 fi
 
 if ! grep 'try-import %workspace%/.local_cuda.bazelrc' "${SRC_PATH_JAX}/.bazelrc"; then
-  echo 'try-import %workspace%/.local_cuda.bazelrc' >> "${SRC_PATH_JAX}/.bazelrc"
+  echo -e '\ntry-import %workspace%/.local_cuda.bazelrc' >> "${SRC_PATH_JAX}/.bazelrc"
 fi
 cat > "${SRC_PATH_JAX}/.local_cuda.bazelrc" << EOF
 build:cuda --repo_env=LOCAL_CUDA_PATH="/usr/local/cuda"