QtWebEngine 5.11-rc2 doesn't compile on clang armv7hnl

QtWebEngine 5.11.0-rc2 builds fine on x86_64 and i686, but fails on ARM platforms.

On 32-bit (armv7hnl):

../../../../src/3rdparty/chromium/third_party/skia/src/jumper/SkJumper_stages.cpp:692:19: error: functional-style cast from 'F' (aka 'V<float>') to '__fp16' is not allowed

__fp16 fp16 = __fp16(f);

^~~~~~~~ 1 error generated.

On 64-bit (aarch64):

../../../../src/3rdparty/chromium/mojo/public/cpp/bindings/associated_interface_ptr_info.h:48:43: error: cannot convert 'const mojo::ScopedInterfaceEndpointHandle' to 'bool' in return

explicit operator bool() const { return handle_; }

                                                           ^~~~~~~

The latter failure doesn't look arch specific, more likely caused by gcc 8.1.0