[LyX/master] Fix configure with Qt 6.1

[Enrico Forestieri]

commit f60b23cbc11f92eba7b14d371bcb2625a0fda998
Author: Enrico Forestieri <forenr at lyx.org>
Date:   Tue Jun 15 11:40:27 2021 +0200

    Fix configure with Qt 6.1
    
    Since Qt 6.1 the moc, rcc, and uic compilers are not installed
    in the bin dir anymore. We ask qmake for their location and
    record them with full path so that it is not necessary thinkering
    with the PATH variable.
---
 config/qt.m4 |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/config/qt.m4 b/config/qt.m4
index 33152ce..7fe329f 100644
--- a/config/qt.m4
+++ b/config/qt.m4
@@ -80,7 +80,9 @@ AC_DEFUN([QT_FIND_TOOL],
 	fi
 	qt_ext="qt$qt_major"
 
-	if test -n "$qt_cv_bin" ; then
+	if test -n "$qt_cv_libexec" ; then
+		AC_PATH_PROGS($1, [$2], [], $qt_cv_libexec)
+	elif test -n "$qt_cv_bin" ; then
 		AC_PATH_PROGS($1, [$2], [], $qt_cv_bin)
 	elif qtchooser -l 2>/dev/null | grep -q ^$qt_ext\$ >/dev/null ; then
 		AC_PATH_PROG(qtc_path, qtchooser, [], [$PATH])
@@ -404,6 +406,7 @@ AC_DEFUN([QT6_QMAKE_CONFIG],
 	AC_MSG_CHECKING([for Qt6])
 	qtver=`$QT_QMAKE -v | grep -o "Qt version ."`
 	if test "$qtver" = "Qt version 6"; then
+	    qt_cv_libexec=`$QT_QMAKE -query QT_INSTALL_LIBEXECS`
 	    dnl Use a .pro file for getting qmake's variables
 	    lyx_test_qt_dir=`mktemp -d`
 	    lyx_test_qt_pro="$lyx_test_qt_dir/test.pro"