Qmake doesn't use stdc++11 compilation flag - c++

Question

When I try to compile my project, I've got this error :
g++ -c -pipe -std=c++11 -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic -std=gnu++98 -Wno-deprecated -O2 -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/usr/lib64/qt4/mkspecs/linux-g++ -I. -I/usr/include/QtCore -I/usr/include/QtGui -I/usr/include -I+= -I../includes -I. -I. -o ThreadPool.o ../sources/ThreadPool.cpp
In file included from /usr/include/c++/5.3.1/thread:35:0,
from ../includes/ThreadPool.hpp:4,
from ../sources/ThreadPool.cpp:1:
/usr/include/c++/5.3.1/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the ISO C++ 2011 standard. This support must be enabled with the -std=c++11 or -std=gnu++11 compiler options.
#error This file requires compiler and library support \
I don't understand why because I use the flag -std=c++11 in my Makefile
#-------------------------------------------------
#
# Project created by QtCreator 2016-04-11T18:51:06
#
#-------------------------------------------------
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = plazza_gui
SOURCES += main.cpp\
../sources/Window.cpp \
../sources/ThreadPool.cpp \
../sources/ProcessManager.cpp \
../sources/Process.cpp \
../sources/NamedPipe.cpp \
../sources/Xor.cpp \
../sources/AEncryptionMethod.cpp \
../sources/Cesar.cpp \
../sources/ProcessData.cpp \
../sources/Parser.cpp
HEADERS += ../includes/Window.hpp
INCLUDEPATH += += ../includes/
FORMS += forms/mainwindow.ui
QMAKE_CXXFLAGS += -std=c++11
LIBS += \
-lboost_regex \
DISTFILES += \
ressources/pizzera.jpg \
ressources/pizzeria.png \
ressources/icon.png
RESOURCES += \
ressources/ico.qrc
The Makefile works fine in my friend's computer, but when I clone it I can't compile it.

Answer 1

That means your compiler does not support c++11 in that way. Try this if you are sure your compiler is not that old:
CONFIG += c++11