dunno if you managed to resolve your problem in the meantime,
but I had a similar error (under macOS and emscripten 1.39.17):

After downloading and installing everything, I ran emsdk_env (which should generate the ~/.emscripten file in the user folder, if I remember correctly)

But it seems, that Qt Creator could not resolve the var for the defined emsdk_path

emsdk_path = os.path.dirname(os.environ.get('EM_CONFIG')).replace('\\', '/')

so I replaced all the placeholder with the explicit path:

emsdk_path = '/Users/myuser/Documents/Programming/emsdk'

I also added

COMPILER_ENGINE = NODE_JS JS_ENGINES = [NODE_JS]

at the bottom (not sure though if that was needed)

After restarting Qt creator the compiler and toolkit for WebAssembly wer successfully recognized.

@SherifOmran said in how to compile qt static with open ssl:

PATH

If you really need to change that variable, then do it only in the terminal you use to build your stuff. It's never a good idea to add the path to such sensitive libraries system wide as you might break unrelated applications.

Everything is correct. I have reinstalled and these three buttons are
done by as you already stated. Thanks! It was two reasons.
THANKS!!!

I meet the same issue today. So i download the older version of Qt.

solved it by doing:

sudo apt-get install mesa-common-dev

and by removing and copying over src/gui dir

@Henrinacio so you don't have the correct version of Visual Studio installed. You installed Qt for Visual Studio 2012 and 2013. On Windows you can't just mix and match like that. The different version of Visual Studio are not compatible one with the other. So you have two solutions:

Install VS2013 to use Qt for MSVC2013 Build Qt yourself with VS2015

Just did mark it as solved.
This might be because you have signed up lately. Not sure what the restrictions are, but it is meant for spam prevention.

Otherwise at your top post respectively any other post you should see a gear wheel at the right. Click on this and on the left button showing up. In general it is self-explanatory and I am sure you will find it next time.