I had the exact same problem when I tried to compile OpenCV with Qt Creator (MinGW) to build the .a static library files.
For those that installed Qt 5.2.1 for Windows 32-bit (MinGW 4.8, OpenGL, 634 MB), this problem can be fixed if you add the following to the system's environment variable Path
:
C:\Qt\Qt5.2.0\Tools\mingw48_32\bin