Starting with Bazel 0.21 the --experimental_strict_action_env option has been renamed to --incompatible_strict_action_env and is now on by default. This means Bazel will no longer use the client's PATH and LD_LIBRARY_PATH environmental variables in the default action environment. If the old behavior is desired, pass --action_env=PATH and --action_env=LD_LIBRARY_PATH. --noincompatible_strict_action_env will also temporarily restore the old behavior. However, as --action_env is a more general and explicit way to pass client environmental variables into actions, --noincompatible_strict_action_env will eventually be deprecated and removed. See #6648 for more details.

Both flag names --experimental_strict_action_env and --incompatible_strict_action_env will keep working for a few releases.

Also see #2574

cc: @benjaminp