[LyX/2.4.x] Avoid bogus warnings when configuring for Qt6

[Enrico Forestieri]

commit 94004da71f919e819271925924f0a5784f7305fc
Author: Enrico Forestieri <forenr at lyx.org>
Date:   Wed Jul 3 21:02:51 2024 +0200

    Avoid bogus warnings when configuring for Qt6
    
    Recent versions of qmake complain loudly when the locale
    does not explicitly specify the utf8 codeset. Specifically,
    the configure script exports LC_ALL=C and that implies the
    ascii codeset. Previously, this was silently changed to utf8,
    whereas now we get a warning for each qmake invocation.
    So, explicitly set utf8 before calling qmake.
---
 config/qt.m4 | 4 ++++
 status.24x   | 1 +
 2 files changed, 5 insertions(+)

diff --git a/config/qt.m4 b/config/qt.m4
index 7e7ffd6df2..96810bfc9b 100644
--- a/config/qt.m4
+++ b/config/qt.m4
@@ -379,6 +379,10 @@ AC_DEFUN([QT6_QMAKE_CONFIG],
 [
 	dnl Use first suitable qmake in PATH
 	AC_CHECK_PROGS([QT_QMAKE], [qmake-qt6 qmake6], [qmake], $PATH)
+	case ${host} in
+	*mingw*) ;;
+	*) QT_QMAKE="env LC_ALL=C.UTF-8 $QT_QMAKE" ;;
+	esac
 	AC_MSG_CHECKING([for Qt6])
 	qtver=`$QT_QMAKE -v | grep -o "Qt version ."`
 	if test "$qtver" = "Qt version 6"; then
diff --git a/status.24x b/status.24x
index 702f13f5b8..cb0810c0f2 100644
--- a/status.24x
+++ b/status.24x
@@ -35,6 +35,7 @@ What's new
 
 * BUILD/INSTALLATION
 
+- Avoid bogus warnings when configuring for Qt6.