Qt6 wasm build from sources: error: unknown type name 'Q_DECLARE_METATYPE'

commit 2a036a7594e6689d18be65e8a75ef23abb412bbc (HEAD -> 6.0.0, tag: v6.0.0-rc1, origin/6.0.0)
Author: Qt Submodule Update Bot <qt_submodule_update_bot@qt-project.org>
Date:   Tue Nov 24 21:18:47 2020 +0200

make[3]: Entering directory '/qt5/qtlottie/src/bodymovin'
em++ -c -pipe -O2 -std=c++1z -fvisibility=hidden -fvisibility-inlines-hidden -fno-exceptions -s ALLOW_MEMORY_GROWTH=1 -Wall -Wextra -Wdate-time -Winconsistent-missing-override -DQT_NO_FOREACH -DQT_NO_JAVA_STYLE_ITERATORS -DQT_NO_LINKED_LIST -DBODYMOVIN_LIBRARY -DQT_DEPRECATED_WARNINGS -DQT_NO_NARROWING_CONVERSIONS_IN_CONNECT -DQT_BUILD_BODYMOVIN_LIB -DQT_BUILDING_QT -DQT_NO_CAST_TO_ASCII -DQT_ASCII_CAST_WARNINGS -DQT_MOC_COMPAT -DQT_USE_QSTRINGBUILDER -DQT_DISABLE_DEPRECATED_BEFORE=0x050000 -DQT_DEPRECATED_WARNINGS_SINCE=0x060000 -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -I. -I../../include -I../../include/QtBodymovin -I../../include/QtBodymovin/6.0.0 -I../../include/QtBodymovin/6.0.0/QtBodymovin -I/qt5/qtbase/include/QtGui/6.0.0 -I/qt5/qtbase/include/QtGui/6.0.0/QtGui -I/qt5/qtbase/include -I/qt5/qtbase/include/QtGui -I/qt5/qtbase/include/QtCore/6.0.0 -I/qt5/qtbase/include/QtCore/6.0.0/QtCore -I/qt5/qtbase/include/QtCore -I.moc -I/qt5/qtbase/mkspecs/wasm-emscripten -o .obj/trimpath.o trimpath.cpp
In file included from trimpath.cpp:30:
./trimpath_p.h:91:1: error: unknown type name 'Q_DECLARE_METATYPE'
Q_DECLARE_METATYPE(TrimPath);
^
1 error generated.
shared:ERROR: '/emsdk/upstream/bin/clang++ -target wasm32-unknown-emscripten -D__EMSCRIPTEN_major__=1 -D__EMSCRIPTEN_minor__=39 -D__EMSCRIPTEN_tiny__=8 -D_LIBCPP_ABI_VERSION=2 -Dunix -D__unix -D__unix__ -Werror=implicit-function-declaration -Xclang -nostdsysteminc -Xclang -isystem/emsdk/upstream/emscripten/system/include/libcxx -Xclang -isystem/emsdk/upstream/emscripten/system/lib/libcxxabi/include -Xclang -isystem/emsdk/upstream/emscripten/system/include/compat -Xclang -isystem/emsdk/upstream/emscripten/system/include -Xclang -isystem/emsdk/upstream/emscripten/system/include/libc -Xclang -isystem/emsdk/upstream/emscripten/system/lib/libc/musl/arch/emscripten -Xclang -isystem/emsdk/upstream/emscripten/system/local/include -Xclang -isystem/emsdk/upstream/emscripten/cache/wasm-obj/include -c -pipe -O2 -std=c++1z -fvisibility=hidden -fvisibility-inlines-hidden -fno-exceptions -Wall -Wextra -Wdate-time -Winconsistent-missing-override -DQT_NO_FOREACH -DQT_NO_JAVA_STYLE_ITERATORS -DQT_NO_LINKED_LIST -DBODYMOVIN_LIBRARY -DQT_DEPRECATED_WARNINGS -DQT_NO_NARROWING_CONVERSIONS_IN_CONNECT -DQT_BUILD_BODYMOVIN_LIB -DQT_BUILDING_QT -DQT_NO_CAST_TO_ASCII -DQT_ASCII_CAST_WARNINGS -DQT_MOC_COMPAT -DQT_USE_QSTRINGBUILDER -DQT_DISABLE_DEPRECATED_BEFORE=0x050000 -DQT_DEPRECATED_WARNINGS_SINCE=0x060000 -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -I. -I../../include -I../../include/QtBodymovin -I../../include/QtBodymovin/6.0.0 -I../../include/QtBodymovin/6.0.0/QtBodymovin -I/qt5/qtbase/include/QtGui/6.0.0 -I/qt5/qtbase/include/QtGui/6.0.0/QtGui -I/qt5/qtbase/include -I/qt5/qtbase/include/QtGui -I/qt5/qtbase/include/QtCore/6.0.0 -I/qt5/qtbase/include/QtCore/6.0.0/QtCore -I/qt5/qtbase/include/QtCore -I.moc -I/qt5/qtbase/mkspecs/wasm-emscripten -DEMSCRIPTEN trimpath.cpp -Xclang -isystem/emsdk/upstream/emscripten/system/include/SDL -c -o .obj/trimpath.o -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr' failed (1)

./configure -xplatform wasm-emscripten -nomake examples -prefix /usr/local/wasm -opensource -confirm-license  -qmake

em++ --version
emcc (Emscripten gcc/clang-like replacement) 1.39.8 (commit 372fb501244f29734b61f889a2ef24c2456a3484)
Copyright (C) 2014 the Emscripten authors (see AUTHORS.txt)
This is free and open source software under the MIT license.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.