The following commands in WebCore/WebCore.pro can corrupt QtWebKit.pc: lib_replace.match = $$DESTDIR lib_replace.replace = $$[QT_INSTALL_LIBS] QMAKE_PKGCONFIG_INSTALL_REPLACE += lib_replace The problem is that .match/.replace doesn't replace plain strings but regular expressions. If $$DESTDIR == "../lib", the resulting command is: sed -e "s,../lib,/usr/lib,g" "../lib/pkgconfig/QtWebKit.pc" >"/build/buildd/qtwebkit-4.7~beta1/debian/tmp/usr/lib/pkgconfig/QtWebKit.pc" "." matches any character so "libdir=${prefix}/lib" is being replaced by "libdir=${prefi/usr/lib". I'm not sure why this path replacement is needed at all.
*** This bug has been marked as a duplicate of bug 36826 ***