add additional err handling for get_git_commit_hash

lm_eval/utils.py

@@ -328,9 +328,10 @@ def get_git_commit_hash():
     Source: https://github.com/EleutherAI/gpt-neox/blob/b608043be541602170bfcfb8ec9bf85e8a0799e0/megatron/neox_arguments/neox_args.py#L42
     """
     try:
-        git_hash = subprocess.check_output(["git", "describe", "--always"]).strip()
+        git_hash = subprocess.check_output(["gt", "describe", "--always"]).strip()
         git_hash = git_hash.decode()
-    except subprocess.CalledProcessError:
+    except subprocess.CalledProcessError or FileNotFoundError:
+        # FileNotFoundError occurs when git not installed on system
         git_hash = None
     return git_hash