CMake: Make sure to install Qt3rdPartyLibraryConfig.cmake.in

Repos like qtshadertools need it when configuring their own
bundled libraries.

Amends 572c03eb7a583baf1f48e5144d2868e5588d292a

Change-Id: I540e99d5bd2938299a10220a1a5e0d97091077b3
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

cmake/QtBaseGlobalTargets.cmake

@@ -281,6 +281,7 @@ qt_internal_export_modern_cmake_config_targets_file(TARGETS ${__export_targets}
 ## Install some QtBase specific CMake files:
 qt_copy_or_install(FILES
                    cmake/ModuleDescription.json.in
+                   cmake/Qt3rdPartyLibraryConfig.cmake.in
                    cmake/QtBuild.cmake
                    cmake/QtBuildInformation.cmake
                    cmake/QtCompilerFlags.cmake