Build failure on Linux with clang++

qtwebengine 5.9.0 fails to build with clang/clang++ on Linux with the following error:

clang++ -c -pipe -stdlib=libc++ -O2 -fPIC -std=gnu+11 -fno-exceptions -Wall -W -D_REENTRANT -DBUILDING_CHROMIUM -DNOMINMAX -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -DQT_WEBENGINECOREHEADERS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I. -I../../core -I../../3rdparty/chromium -isystem /usr/include/qt5 -isystem /usr/include/qt5/QtGui -isystem /usr/include/qt5/QtNetwork -isystem /usr/include/qt5/QtCore/5.9.0 -isystem /usr/include/qt5/QtCore/5.9.0/QtCore -isystem /usr/include/qt5/QtCore -I../../../include -I../../../include/QtWebEngineCore -I../../../include/QtWebEngineCore/5.9.0 -I../../../include/QtWebEngineCore/5.9.0/QtWebEngineCore -I.moc -isystem /usr/include/libdrm -I/usr/lib/qt5/mkspecs/linux-clang-libc+ -o .obj/qtbug-60565.o qtbug-60565.cpp
qtbug-60565.cpp:90:14: warning: unused function 'ShimCppNew' [-Wunused-function]
static void* ShimCppNew(size_t size) {
^
qtbug-60565.cpp:94:14: warning: unused function 'ShimCppNewArray' [-Wunused-function]
static void* ShimCppNewArray(size_t size) {
^
qtbug-60565.cpp:98:13: warning: unused function 'ShimCppDelete' [-Wunused-function]
static void ShimCppDelete(void* address) {
^
qtbug-60565.cpp:102:13: warning: unused function 'ShimCppDeleteArray'
[-Wunused-function]
static void ShimCppDeleteArray(void* address) {
^
qtbug-60565.cpp:55:5: error: alias must point to a defined variable or function
SHIM_ALIAS_SYMBOL(ShimCppNew);
^
qtbug-60565.cpp:49:52: note: expanded from macro 'SHIM_ALIAS_SYMBOL'
#define SHIM_ALIAS_SYMBOL(fn) _attribute_((weak, alias(#fn)))