rust-utils: use new find_dirs iterator
In
cad3dde7a573, the `find_dirs` util was introduced, but the second changeset
that made use of it didn't apply. This change fixes the issue.
Differential Revision: https://phab.mercurial-scm.org/D6639
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true
[*.t]
indent_size = 2
indent_style = space
trim_trailing_whitespace = false