util/lint: Apply `final newlines` check to scripts

The `lint-extended-015-final-newlines` script skips over executable
files and thus leaves script files unchecked.

Use `file` to find scripts and include them in the `final newlines`
checks. Whitelisting is used including bash, perl, python and sh
scripts.

Change-Id: I8649b261b7e2cbbac7f9b90a9ace3f1c7b0eedeb
Signed-off-by: Alex Thiessen <alex.thiessen.de+coreboot@gmail.com>
Reviewed-on: https://review.coreboot.org/23325
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

util/lint/lint-extended-015-final-newlines

@@ -28,10 +28,27 @@ else
 	FIND_FILES="find . "
 fi
 
+HAVE_FILE=$(command -v file 1>/dev/null 2>&1; echo $?)
+
+is_eligible_executable() {
+	if [ "$HAVE_FILE" -ne 0 ]; then
+		return 1
+	fi
+	if { LC_ALL=C; file --brief "$filename" | grep -Eqw \
+		"^(Bourne shell|POSIX shell|Perl|Python) script"; };
+	then
+		return 0
+	else
+		return 1
+	fi
+}
+
 test_for_final_newline() {
 	while read filename; do
-		# Only check non-executable regular files
-		if [ -f "$filename" ] && [ ! -x "$filename" ]; then
+		# Only check regular files and script executables
+		if [ -f "$filename" ] && { [ ! -x "$filename" ] || \
+			is_eligible_executable "$filename"; };
+		then
 
 			# Verify that there is a newline at the end
 			# $() strips trailing newlines