[LyX/master] Improve detection of Qt6 libs

[Enrico Forestieri]

commit 4d71d3d8a745269363b6b8db9e59beaac599ad89
Author: Enrico Forestieri <forenr at lyx.org>
Date:   Sat Oct 16 19:09:30 2021 +0200

    Improve detection of Qt6 libs
    
    We would miss the libraries specified by a full path when
    also '-L' flags are present, as we would only take into
    account those specified by '-l' flags.
---
 config/qt.m4 |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/config/qt.m4 b/config/qt.m4
index cfd6a59..99f43a2 100644
--- a/config/qt.m4
+++ b/config/qt.m4
@@ -454,7 +454,7 @@ EOF2
 		    QT_LDFLAGS="-L`$QT_QMAKE -query QT_INSTALL_LIBS`"
 		    QT_LIB="$qt_guilibs"
 		else
-		    QT_LIB=`echo $qt_guilibs | tr ' ' '\n' | grep -e "^-l" | tr '\n' ' '`
+		    QT_LIB=`echo $qt_guilibs | tr ' ' '\n' | grep -v "^-L" | tr '\n' ' '`
 		fi
 		QTLIB_VERSION=`$QT_QMAKE -v | grep "Qt version" | sed -e 's/.*\([[0-9]]\.[[0-9]]*\.[[0-9]]\).*/\1/'`
 		if test -z "$QT_LIB"; then