Make use of all Qt features conditional that are not supported on the
web assembly platform (mainly TLS support and QProcess).
Note that HTTPs is supposed to work nevertheless as long as the certificate
matches (with the usual corss-site scripting limitations).
It looks like `libstdc++` and `libc++` only define this `enum class` member
when the `ETIME` macro is defined. To prevent build errors when this macro
is not defined it makes sense to check for this error only conditionally.
Not sure why `QString::toStdWString()` doesn't work with this compiler and
the official Qt 6.5.0 build. However, instantiating an `std::wstring`
manually works so let's just use this as a workaround.
Note that with GCC/mingw-w64 and Qt 6.4.3 the `QString::toStdWString()`
function works just fine.