Fails to build on macOS: fatal error: 'QtUiPlugin/QDesignerCustomWidgetInterface' file not found

cd qwebengineview/ && ( test -e Makefile || /usr/local/Qt-5.8.0/bin/qmake -o Makefile /Users/flo/build/qtwebengine-opensource-src-5.8.0/src/plugins/qwebengineview/qwebengineview.pro WEBENGINE_CONFIG+=use_proprietary_codecs ) && /Applications/Xcode.app/Contents/Developer/usr/bin/make -f Makefile
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -c -pipe -stdlib=libc++ -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -mmacosx-version-min=10.7  -O2 -std=c++1z -fvisibility=hidden -fvisibility-inlines-hidden -fno-exceptions -Wall -W -fPIC -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NO_DEBUG -DQT_PLUGIN -DQT_WEBENGINEWIDGETS_LIB -DQT_WEBENGINECORE_LIB -DQT_DESIGNER_LIB -DQT_UIPLUGIN_LIB -DQT_PRINTSUPPORT_LIB -DQT_WIDGETS_LIB -DQT_QUICK_LIB -DQT_GUI_LIB -DQT_XML_LIB -DQT_WEBCHANNEL_LIB -DQT_QML_LIB -DQT_NETWORK_LIB -DQT_POSITIONING_LIB -DQT_CORE_LIB -DQDESIGNER_EXPORT_WIDGETS -I. -I../../../include -I../../../include/QtWebEngineWidgets -I../../../include/QtWebEngineCore -I/usr/local/Qt-5.8.0/lib/QtDesigner.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtUiPlugin.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtPrintSupport.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtWidgets.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtQuick.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtGui.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtXml.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtWebChannel.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtQml.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtNetwork.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtPositioning.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtCore.framework/Headers -I.moc -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/OpenGL.framework/Headers -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/AGL.framework/Headers -I/usr/local/Qt-5.8.0/mkspecs/macx-clang -F/Users/flo/build/qtwebengine-opensource-src-5.8.0/lib -F/usr/local/Qt-5.8.0/lib -o .obj/qwebengineview_plugin.o qwebengineview_plugin.cpp
/usr/local/Qt-5.8.0/bin/rcc -name qwebengineview_plugin qwebengineview_plugin.qrc -o .rcc/qrc_qwebengineview_plugin.cpp
In file included from qwebengineview_plugin.cpp:37:
./qwebengineview_plugin.h:40:10: fatal error: 'QtUiPlugin/QDesignerCustomWidgetInterface' file not found
#include <QtUiPlugin/QDesignerCustomWidgetInterface>
         ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -pipe -stdlib=libc++ -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -mmacosx-version-min=10.7  -O2 -std=c++1z -fvisibility=hidden -fvisibility-inlines-hidden -fno-exceptions -Wall -W -dM -E -o .moc/moc_predefs.h /usr/local/Qt-5.8.0/mkspecs/features/data/dummy.cpp
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -c -pipe -stdlib=libc++ -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -mmacosx-version-min=10.7  -O2 -std=c++1z -fvisibility=hidden -fvisibility-inlines-hidden -fno-exceptions -Wall -W -fPIC -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NO_DEBUG -DQT_PLUGIN -DQT_WEBENGINEWIDGETS_LIB -DQT_WEBENGINECORE_LIB -DQT_DESIGNER_LIB -DQT_UIPLUGIN_LIB -DQT_PRINTSUPPORT_LIB -DQT_WIDGETS_LIB -DQT_QUICK_LIB -DQT_GUI_LIB -DQT_XML_LIB -DQT_WEBCHANNEL_LIB -DQT_QML_LIB -DQT_NETWORK_LIB -DQT_POSITIONING_LIB -DQT_CORE_LIB -DQDESIGNER_EXPORT_WIDGETS -I. -I../../../include -I../../../include/QtWebEngineWidgets -I../../../include/QtWebEngineCore -I/usr/local/Qt-5.8.0/lib/QtDesigner.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtUiPlugin.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtPrintSupport.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtWidgets.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtQuick.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtGui.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtXml.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtWebChannel.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtQml.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtNetwork.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtPositioning.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtCore.framework/Headers -I.moc -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/OpenGL.framework/Headers -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/AGL.framework/Headers -I/usr/local/Qt-5.8.0/mkspecs/macx-clang -F/Users/flo/build/qtwebengine-opensource-src-5.8.0/lib -F/usr/local/Qt-5.8.0/lib -o .obj/qrc_qwebengineview_plugin.o .rcc/qrc_qwebengineview_plugin.cpp
/usr/local/Qt-5.8.0/bin/moc -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NO_DEBUG -DQT_PLUGIN -DQT_WEBENGINEWIDGETS_LIB -DQT_WEBENGINECORE_LIB -DQT_DESIGNER_LIB -DQT_UIPLUGIN_LIB -DQT_PRINTSUPPORT_LIB -DQT_WIDGETS_LIB -DQT_QUICK_LIB -DQT_GUI_LIB -DQT_XML_LIB -DQT_WEBCHANNEL_LIB -DQT_QML_LIB -DQT_NETWORK_LIB -DQT_POSITIONING_LIB -DQT_CORE_LIB -DQDESIGNER_EXPORT_WIDGETS --include .moc/moc_predefs.h -I/usr/local/Qt-5.8.0/mkspecs/macx-clang -I/Users/flo/build/qtwebengine-opensource-src-5.8.0/src/plugins/qwebengineview -I/Users/flo/build/qtwebengine-opensource-src-5.8.0/include -I/Users/flo/build/qtwebengine-opensource-src-5.8.0/include/QtWebEngineWidgets -I/Users/flo/build/qtwebengine-opensource-src-5.8.0/include/QtWebEngineCore -I/usr/local/Qt-5.8.0/lib/QtDesigner.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtUiPlugin.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtPrintSupport.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtWidgets.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtQuick.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtGui.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtXml.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtWebChannel.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtQml.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtNetwork.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtPositioning.framework/Headers -I/usr/local/Qt-5.8.0/lib/QtCore.framework/Headers -I/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1 -I/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/7.0.2/include -I/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include -F/Users/flo/build/qtwebengine-opensource-src-5.8.0/lib -F/usr/local/Qt-5.8.0/lib qwebengineview_plugin.h -o .moc/moc_qwebengineview_plugin.cpp
qwebengineview_plugin.h:82: Error: Undefined interface