FTBFS for QtWebKit: "ICU is required"

Steps to reproduce:

1. Install ICU to somewhere standard (e.g., on Windows C:\Qt\icu)
2. Configure qtbase:
   • On Windows: configure -Ic:/qt/icu/include -Lc:/qt/icu/lib64
   • Elsewhere: normal, just make sure sure qtbase can find ICU
3. Compile qtbase (note how it finds ICU and links to it)
4. Run qmake in qtwebkit

It prints, at the end:

The WebKit build was disabled for the following reasons:
    * ICU is required.