[LyX/master] Use -Wno-deprecated-copy also with clang++ 11

[Jean-Marc Lasgouttes]

commit 24fb0ff8efb867f80ab3b9e87c9401499eee409b
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Mon Oct 5 18:17:40 2020 +0200

    Use -Wno-deprecated-copy also with clang++ 11
---
 config/lyxinclude.m4 |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/config/lyxinclude.m4 b/config/lyxinclude.m4
index 369ecae..a943ddd 100644
--- a/config/lyxinclude.m4
+++ b/config/lyxinclude.m4
@@ -410,7 +410,7 @@ if test x$GXX = xyes; then
   if test x$enable_warnings = xyes ; then
       AM_CPPFLAGS="$AM_CPPFLAGS -Wall -Wextra"
       case $gxx_version in
-	  9.*|10.*|clang-10*)
+	  9.*|10.*|clang-10*|clang-11*)
 	      AM_CXXFLAGS="$AM_CXXFLAGS -Wno-deprecated-copy";;
 	  *);;
       esac