Rather than fail with obscure can't find Qt packages errors when the
Webassembly CMake toolchain file can not be found, error out with a
clear error on how to ensure it is found.
Pick-to: 6.2
Task-number: QTBUG-96843
Change-Id: I0f34cdcde05efb25c93017f3fd365186335ed52c
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
Split qt_auto_detect_wasm into multiple helper functions and place
them in a new QtPublicWasmToolchainHelpers.cmake file.
We want to use them to try and detect the CMake toolchain
file location from within the generated qt.toolchain.cmake
file whem configuring a user project.
Pick-to: 6.2
Task-number: QTBUG-96843
Change-Id: Id8c2350e6dbe3c994b435681353bdaee114249a7
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>