Force build with -O2 instead of -O3 on 32-bit linux

cmake/OpenCVCompilerOptions.cmake

-if(MINGW)
+if(MINGW OR (X86 AND UNIX AND NOT APPLE))
   # mingw compiler is known to produce unstable SSE code with -O3 hence we are trying to use -O2 instead
   if(CMAKE_COMPILER_IS_GNUCXX)
     foreach(flags CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_RELEASE CMAKE_CXX_FLAGS_DEBUG)