In my opinion,
git clean -df
should do the trick. As per Git documentation on git clean
git-clean - Remove untracked files from the working tree
Description
Cleans the working tree by recursively removing files that are not under version control, starting from the current directory.
Normally, only files unknown to Git are removed, but if the -x option is specified, ignored files are also removed. This can, for example, be useful to remove all build products.
If any optional ... arguments are given, only those paths are affected.
Options
-d Remove untracked directories in addition to untracked files. If an untracked directory is managed by a different Git repository, it is not removed by default. Use -f option twice if you really want to remove such a directory.
-f --force If the Git configuration variable clean.requireForce is not set to false, git clean will refuse to run unless given -f, -n or -i.