CMake: Make it possible to use qt-cmake with --build and --install

It wasn't possible to use the qt-cmake script with, e.g. the --build or
--install argument, because we called cmake with
-DCMAKE_TOOLCHAIN_FILE=..., and such arguments must be passed as the
first argument.

Since CMake 3.21 it's possible to pass the toolchain file via an
environment variable. This patch changes qt-cmake and qt-cmake.bat
accordingly.

This is safe, because we require CMake 3.22 for building Qt since Qt
6.9.

Pick-to: 6.10
Fixes: QTBUG-140785
Change-Id: I4b4bc729e80a0ab9fbe275cf2d3900111be3c1a3
Reviewed-by: Alexey Edelev <[email protected]>

Author: jobor

bin/qt-cmake.bat.in

@@ -7,5 +7,5 @@ set script_dir_path=%~dp0
 set cmake_path=@CMAKE_COMMAND@
 if not exist "%cmake_path%" set cmake_path=cmake
 
-set toolchain_path=%script_dir_path%\@__GlobalConfig_relative_path_from_bin_dir_to_cmake_config_dir@\qt.toolchain.cmake
-"%cmake_path%" -DCMAKE_TOOLCHAIN_FILE="%toolchain_path%" @__qt_cmake_extra@ %*
+set CMAKE_TOOLCHAIN_FILE=%script_dir_path%\@__GlobalConfig_relative_path_from_bin_dir_to_cmake_config_dir@\qt.toolchain.cmake
+"%cmake_path%" @__qt_cmake_extra@ %*

bin/qt-cmake.in

@@ -16,4 +16,7 @@ toolchain_path="$script_dir_path/@__GlobalConfig_relative_path_from_bin_dir_to_c
 @extra_qt_cmake_code@
 
 # Find the qt toolchain relative to the absolute bin dir path where the script is located.
-exec "$cmake_path" -DCMAKE_TOOLCHAIN_FILE="$toolchain_path" @__qt_cmake_extra@ "$@"
+CMAKE_TOOLCHAIN_FILE="$toolchain_path"
+export CMAKE_TOOLCHAIN_FILE
+
+exec "$cmake_path" @__qt_cmake_extra@ "$@"