More messages:

SOFT ASSERT: "false && "__cplusplus is not predefined, assuming latest C++ we support."" in file /home/qt/work/build/qt-creator/src/plugins/projectexplorer/toolchain.cpp, line 443
SOFT ASSERT: "false && "__cplusplus is not predefined, assuming latest C++ we support."" in file /home/qt/work/build/qt-creator/src/plugins/projectexplorer/toolchain.cpp, line 443
SOFT ASSERT: "d->m_logWindow" in file /home/qt/work/build/qt-creator/src/plugins/debugger/debuggerengine.cpp, line 1756
MSG: "QUIT DEBUGGER REQUESTED IN STATE 16"
SOFT ASSERT: "d->m_logWindow" in file /home/qt/work/build/qt-creator/src/plugins/debugger/debuggerengine.cpp, line 1756
MSG: "126^done"
SOFT ASSERT: "d->m_logWindow" in file /home/qt/work/build/qt-creator/src/plugins/debugger/debuggerengine.cpp, line 1756
MSG: "COOKIE FOR TOKEN 126 ALREADY EATEN (DebuggerFinished). TWO RESPONSES FOR ONE COMMAND?"
SOFT ASSERT: "d->m_logWindow" in file /home/qt/work/build/qt-creator/src/plugins/debugger/debuggerengine.cpp, line 1756
MSG: "(gdb) "
SOFT ASSERT: "d->m_logWindow" in file /home/qt/work/build/qt-creator/src/plugins/debugger/debuggerengine.cpp, line 1756
MSG: "\nNON-CRITICAL TIMEOUT\nCOMMANDS STILL IN PROGRESS: "

It was my fault, the right .pro syntax is:

QMAKE_CFLAGS_DEBUG += -Wno-cpp QMAKE_CXXFLAGS_DEBUG += -Wno-cpp

The precedent syntax removes the -g gcc option from Makefile.

@sneubert Thanks :)

Something's not clear here. Are you trying to cross-compile from Windows to a x86(_64) Linux system ? Or to cross-compile for ARM ?

@okieh

As it looks to me the installation of Qt 5.2.1 is broken. If possible you should also install the newest version of Qt libs IMHO.

However, from personal experience it might be also worthwhile to update your Ubuntu. I am operating a server with Ubuntu 12.04 and had quite a bit of trouble in connection Qt 5 there. Luckily the admin there, "some" version (5.0 or 5.1) to work at least moderately.
On Ubuntu 14.04 on my desktop everything worked like a charm.
Finally I like to state that I am developing on Windows. Therefore, my Linux knowledge is limited as well.