[LyX/master] Disable deprecated-copy warning with clang10

[Jean-Marc Lasgouttes]

commit e9e8069b170ef3128402bc6e6f657339da1760a2
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Tue Apr 28 13:16:45 2020 +0200

    Disable deprecated-copy warning with clang10
    
    This was already done for gcc9 and saves tons of warnings.
    
    Note that the warning in Qt are gone with Qt5.13, so eventually we
    will have to get rid of our own copy issues.
---
 config/lyxinclude.m4 |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/config/lyxinclude.m4 b/config/lyxinclude.m4
index 5ba1984..e3eade8 100644
--- a/config/lyxinclude.m4
+++ b/config/lyxinclude.m4
@@ -408,10 +408,11 @@ if test x$GXX = xyes; then
   fi
   dnl Warnings are for preprocessor too
   if test x$enable_warnings = xyes ; then
+      AM_CPPFLAGS="$AM_CPPFLAGS -Wall -Wextra"
       case $gxx_version in
-	  9.*) AM_CPPFLAGS="$AM_CPPFLAGS -Wall -Wextra"
-	       AM_CXXFLAGS="$AM_CXXFLAGS  -Wno-deprecated-copy";;
-	  *) AM_CPPFLAGS="$AM_CPPFLAGS -Wall -Wextra";;
+	  9.*|clang-10*)
+	      AM_CXXFLAGS="$AM_CXXFLAGS -Wno-deprecated-copy";;
+	  *);;
       esac
     fi
   case $gxx_version in