Pin bazeliskrc to 4.1.0 which supports m1 (#705)

bazelbuild/bazel#11628 is in Release 4.1 - May 2021 #13099

Pin vs rm for build repeatability.

.bazeliskrc

@@ -2,5 +2,6 @@
 # Exceptions. See /LICENSE for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-# TODO: Return to a released version as soon as M1 macOS is supported.
-USE_BAZEL_VERSION=latest
+# Keep pinned to a recent release, listed at
+# https://github.com/bazelbuild/bazel.
+USE_BAZEL_VERSION=4.1.0