git: 9c43d5ca20d7 - main - CONTRIBUTING.md: Suggest using checkstyle9.pl

The branch main has been updated by imp:

URL: https://cgit.FreeBSD.org/src/commit/?id=9c43d5ca20d71af5b0885ab2d70e8246f988bb06

commit 9c43d5ca20d71af5b0885ab2d70e8246f988bb06
Author:     Warner Losh <imp@FreeBSD.org>
AuthorDate: 2023-03-21 08:08:12 +0000
Commit:     Warner Losh <imp@FreeBSD.org>
CommitDate: 2023-03-21 08:08:12 +0000

    CONTRIBUTING.md: Suggest using checkstyle9.pl
---
 CONTRIBUTING.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index ad221be66afc..8aedda5f4e69 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -29,6 +29,7 @@ A pull request will be considered if:
 * Fixup commits should be squashed with the commit they are fixing. Each commit in your branch should be suitable for FreeBSD's repository.
 * Commits should include one or more `Signed-off-by:` lines with full name and email address certifying [Developer Certificate of Origin](https://developercertificate.org/).
 * The commits follow FreeBSD's style guide. See [Style](#Style).
+* Run tools/build/checkstlye9.pl on your git branch and eliminate all errors
 * The commits should not introduce trailing white space.
 * If the commmit fixes a bug, please add 'PR: <bugnumber>' to the comment message.
 * If there's a code review in phabricator, please include a link as a 'Differential Revision: ' line.