[LyX/master] Fix build with Qt6

[Enrico Forestieri]

commit 47f1fec96cbde8a6da739a9bedb4b22df0027976
Author: Enrico Forestieri <forenr at lyx.org>
Date:   Tue Oct 12 20:23:27 2021 +0200

    Fix build with Qt6
    
    In Qt6 the Svg includes are split into two different subdirs,
    namely QtSvg and QtSvgWidgets. So, after 0862042b, it is necessary
    to also account for the last one. Nothing needs to be done for Qt5.
---
 config/qt.m4 |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/config/qt.m4 b/config/qt.m4
index d41332a..cfd6a59 100644
--- a/config/qt.m4
+++ b/config/qt.m4
@@ -440,6 +440,7 @@ qtHaveModule(core5compat):	QT += core5compat
 qtHaveModule(concurrent):	QT += concurrent
 qtHaveModule(gui):		QT += gui
 qtHaveModule(svg):		QT += svg
+qtHaveModule(svgwidgets):	QT += svgwidgets
 qtHaveModule(widgets):		QT += widgets
 percent.target = %
 percent.commands = @echo -n "\$(\$(@))\ "