make mkl link to threaded version with GCC (pytorch#958)

Author: ngimel

cmake/FindMKL.cmake

@@ -50,7 +50,7 @@ ENDIF ("${SIZE_OF_VOIDP}" EQUAL 8)
 IF(CMAKE_COMPILER_IS_GNUCC)
  SET(mklthreads "mkl_gnu_thread" "mkl_intel_thread")
  SET(mklifaces "gf" "intel")
- SET(mklrtls)
+ SET(mklrtls "iomp5")
 ELSE(CMAKE_COMPILER_IS_GNUCC)
  SET(mklthreads "mkl_intel_thread")
  SET(mklifaces "intel")