After more than a year I have been compiling Qt with clang, now I can honestly say it compiles and runs. Not only I can bootstrap clang properly, and it compiles the core Qt4, but it also compiles the WebKit module (and runs flash!), I also saw on the console messages about JDK being loaded, so the browser demo seems very functional to me:
I have also tested the browser using the SubSpider test, and I see that the browser is not that slow (QtSDK/64bit from Nokia runs at 360.0ms +/- 2.5%, and the compiled one in 415.4ms +/- 3.6%, Chromium runs at 249.2ms +/- 11.0%).
As a special bonus, I decided to build Qt-Creator. It compiles and works quite good. I assume you can even use the new toolchain to compile applications, even tough that the error messages will not be recognized by the IDE.
I will try to clean up my build scripts so I can publish it online. I am also thinking of releasing the results as a "qt-clang-sdk" or something. Is anyone interested in such thing?