util/lint: Check for windows line endings

The codebase currently has only unix line endings, so add a lint tool
to check for windows line endings.

BUG=None
TEST=Verify that line endings are caught both inside and outside a git
repo.

Signed-off-by: Martin Roth <martin@coreboot.org>
Change-Id: I6faf99a3184e4843640fb8965f8124de0bc52ce7
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50851
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

util/lint/lint-stable-026-line-endings

@@ -0,0 +1,20 @@
+#!/usr/bin/env sh
+#
+# SPDX-License-Identifier: GPL-2.0-only
+
+# DESCR: Verify that files don't contain windows line endings
+
+LC_ALL=C export LC_ALL
+
+EXCLUDE='^3rdparty/\|^payloads/external\|^.git'
+
+# Use git grep if the code is in a git repo, otherwise use grep.
+if [ -n "$(command -v git)" ] && \
+	[ "$(git rev-parse --is-inside-work-tree 2>/dev/null)" = "true" ]
+then
+	GREP_FILES="git grep -IlP"
+else
+	GREP_FILES="grep -rIlP"
+fi
+
+${GREP_FILES} "\r$" | grep -v "$EXCLUDE"