[LyX/master] Fix compilation with gcc-12

[José Matos]

commit b73ab0256d113571174fed4b2a3405fe8c44d297
Author: José Matos <jamatos at lyx.org>
Date:   Thu Jan 27 15:37:45 2022 +0000

    Fix compilation with gcc-12
---
 src/insets/InsetListings.cpp |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/src/insets/InsetListings.cpp b/src/insets/InsetListings.cpp
index 57df06e..67a0462 100644
--- a/src/insets/InsetListings.cpp
+++ b/src/insets/InsetListings.cpp
@@ -41,6 +41,7 @@
 #include "frontends/alert.h"
 #include "frontends/Application.h"
 
+#include <cstring>
 #include <regex>
 #include <sstream>