fix: adds dockerfile check dir to git safe dir list

[marshallford]

I discovered this issue while "mocking" the git command used to find files in order to troubleshoot the difference between the container image published for 2.4.0 and 2.7.0. As it turns out, a newer version of git (bundled with the container image) now errors on unsafe directories causing ec to check all files in the directory (including those git ignored).

/check # git ls-files --cached --others --modified --exclude-standard
fatal: detected dubious ownership in repository at '/check'
To add an exception for this directory, call:

	git config --global --add safe.directory /check