Fix OSS bazel build on MacOS

see https://github.com/bazelbuild/bazel/issues/10472 for more info on
why this is needed. Without it, the build will try to use system
headers which conflict with project defined headers in this build
for boringssl

.bazelrc

@@ -1,3 +1,4 @@
 build --action_env=BAZEL_CXXOPTS=-std=c++17
 # Definition of --config=memcheck
-build:memcheck --strip=never --test_timeout=3600
+build:memcheck --strip=never --test_timeout=3600
+build --sandbox_block_path=/usr/local