[fbsync] Fixing issue with setup_env.sh in docker (#6106)

Summary:
New version of git checks folder owner and errors with 'fatal: unsafe repository' if owner is different.
Thus, `root_dir="$(git rev-parse --show-toplevel)"` is failing.

To fix the issue, just added all floder as safe directories
git rev-parse --show-toplevel

Reviewed By: NicolasHug

Differential Revision: D36760912

fbshipit-source-id: f2220269833e0cf25beafa71dba84709fe0113e2

.circleci/unittest/linux/scripts/setup_env.sh

@@ -8,6 +8,8 @@
 set -e
 
 this_dir="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
+# Avoid error: "fatal: unsafe repository"
+git config --global --add safe.directory '*'
 root_dir="$(git rev-parse --show-toplevel)"
 conda_dir="${root_dir}/conda"
 env_dir="${root_dir}/env"