doc: robustify PDF build

In some environment like the current dpdk.org server,
there can be some errors due to symbols in titles,
as it was the case before this commit in DPDK 18.05:
commit 551d148944dc ("doc: remove flow API migration section")

	! LaTeX Error: Bad math environment delimiter.

It can be avoided thanks to the Latex command \robustify.

Cc: stable@dpdk.org
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: John McNamara <john.mcnamara@intel.com>

diff --git a/doc/guides/conf.py b/doc/guides/conf.py
index a85f6c9..6d5001a 100644 (file)
--- a/doc/guides/conf.py
+++ b/doc/guides/conf.py
@@ -67,6 +67,9 @@ custom_latex_preamble = r"""
 \usepackage{helvet}
 \renewcommand{\familydefault}{\sfdefault}
 \RecustomVerbatimEnvironment{Verbatim}{Verbatim}{xleftmargin=5mm}
+\usepackage{etoolbox}
+\robustify\(
+\robustify\)
 """
 
 # Configuration for the latex/pdf docs.