[LyX/master] Cmake bqt6 build: Ignore missing Qt6MacExtras

[Kornel Benko]

commit 9b03680ab58e27c3fdcfd1f45a3aa03574f48adf
Author: Kornel Benko <kornel at lyx.org>
Date:   Thu Mar 25 17:29:24 2021 +0100

    Cmake bqt6 build: Ignore missing Qt6MacExtras
---
 CMakeLists.txt |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 12dd394..e4ed8cf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -790,7 +790,11 @@ if(LYX_USE_QT MATCHES "QT6|QT5")
 	if (${QtVal}Core_FOUND)
 		find_package(${QtVal}Widgets CONFIG REQUIRED)
 		if(APPLE)
-			find_package(${QtVal}MacExtras CONFIG REQUIRED)
+			if (LYX_USE_QT MATCHES "QT6")
+				find_package(${QtVal}MacExtras CONFIG QUIET)
+			else()
+				find_package(${QtVal}MacExtras CONFIG REQUIRED)
+			endif()
 		endif()
 		find_package(${QtVal}X11Extras CONFIG QUIET)
 		find_package(${QtVal}WinExtras CONFIG QUIET)