docs: scripts/sphinx-pre-install: suggest latexmk for building pdf

The usage of latexmk improves the PDF output, as it re-run
xelatex when it detects the need, in order to properly generate
indexes and cross-references.

As this is not a mandatory requirement, only suggest its
addition.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/scripts/sphinx-pre-install b/scripts/sphinx-pre-install
index 0674597..f6a5c0b 100755 (executable)
--- a/scripts/sphinx-pre-install
+++ b/scripts/sphinx-pre-install
@@ -532,6 +532,7 @@ sub check_needs()
        check_program("dot", 1);
        check_program("convert", 1);
        check_program("rsvg-convert", 1) if ($pdf);
+       check_program("latexmk", 1) if ($pdf);
 
        check_distros();