There is a mispelled library for your release build:
-clsfml-window
This is my pro file for statically linked projects:
TEMPLATE = app
CONFIG += console c++14
CONFIG -= app_bundle
CONFIG -= qt
DEFINES += SFML_STATIC
LIBS += -Ld:/libraries/lib
INCLUDEPATH += d:/libraries/include
CONFIG(release, debug|release): LIBS += -lsfml-graphics-s -lfreetype -ljpeg -lsfml-window-s -lopengl32 -lgdi32 -lsfml-system-s -lwinmm
CONFIG(debug, debug|release): LIBS += -lsfml-graphics-s-d -lfreetype -ljpeg -lsfml-window-s-d -lopengl32 -lgdi32 -lsfml-system-s-d -lwinmm
SOURCES += main.cpp