Here is a complete CMakeList.txt to reproduce the issue.
#> cat CMakeLists.txt
project(demo)
cmake_minimum_required(VERSION 2.8)
find_package(Qt4 COMPONENTS QtWebKit REQUIRED )
message(STATUS "Test status" ${QT_QTWEBKIT_FOUND} ${QT_QTWEBKIT_INCLUDE_DIR} ${QT_QTWEBKIT_LIBRARY})
Looks like the issue is related to multi-arch support in libqtwebkit-dev because libQtWebKit.so is missed from /usr/lib/x86_64-linux-gnu
#> dpkg -L libqtwebkit-dev | grep '/usr/lib'
/usr/lib
/usr/lib/pkgconfig
/usr/lib/pkgconfig/QtWebKit.pc
/usr/lib/libQtWebKit.prl
/usr/lib/qt4
/usr/lib/qt4/plugins
/usr/lib/qt4/plugins/designer
/usr/lib/qt4/plugins/designer/libqwebview.so
/usr/lib/libQtWebKit.so
#> dpkg -l libqtwebkit-dev
ii libqtwebkit-dev 2.2.0-3 Web content engine library for Qt - development files
The following workaround 'fixes' the issue until the package is really fixed:
#> sudo ln -s /usr/lib/libQtWebKit.so /usr/lib/x86_64-linux-gnu
Hopefully it helps to fix the issue.
BR, Eugene Agafonov