QInotifyFileSystemWatcherEngine::create

error1:
libQtCore.so: undefined reference to `QInotifyFileSystemWatcherEngine::create()'

resolution:
edit ./src/corelib/io/io.pri
find linux-*:
append your cross-toolchain's prefix after it

eg:
my toolchains's prefix is arm_xxxxx
so....
 68        linux-*|arm*:{
 69             SOURCES += /
 70                     io/qfilesystemwatcher_inotify.cpp /
 71                     io/qfilesystemwatcher_dnotify.cpp
 72
 73             HEADERS += /
 74                     io/qfilesystemwatcher_inotify_p.h /
 75                     io/qfilesystemwatcher_dnotify_p.h
 76         }

error2:
libQtCore.so: undefined reference to `clock_gettime'

resolution:
append "-lrt" parameters after the "./configure" so that the compiler can find the define in librt.