QtWebKit's .pri files break cross-compilation by hard-coding /usr/* instead of using $$QT_MODULE_*_BASE.

I created a cross-compilation SDK and set up Qt Creator to use said SDK by following https://developer.toradex.com/knowledge-base/how-to-set-up-qt-creator-to-cross-compile-for-embedded-linux. When trying to cross-compile a project which uses WebKit, I encountered issues, and tracked it down to the .pri files.

Most files in <sdk_root>/sysroots/aarch64-poky-linux/usr/lib/qt5/mkspecs/modules/ contain something like this:

QT.widgets.includes = $$QT_MODULE_INCLUDE_BASE $$QT_MODULE_INCLUDE_BASE/QtWidgets

However, qt_lib_webkit.pri, qt_lib_webkitwidgets.pri, and qt_lib_webkit_private.pri hard-code /usr/include instead of $$QT_MODULE_INCLUDE_BASE, /usr/bin instead of $$QT_MODULE_BIN_BASE, and /usr/lib instead of $$QT_MODULE_LIB_BASE. This makes cross compilation impossible when using QtWebKit.