cmake: guard scanning of default MKL system-wide paths

- WITH_MKL option is enabled
- user doesn't specify MKLROOT/MKL_ROOT_DIR variables

cmake/OpenCVFindLibsPerf.cmake

@@ -2,31 +2,6 @@
 #  Detect other 3rd-party performance and math libraries
 # ----------------------------------------------------------------------------
 
-# --- Lapack ---
-# if(WITH_LAPACK)
-#   if(WIN32)
-#     set(BLA_STATIC 1)
-#   endif()
-#   find_package(LAPACK)
-#   if(LAPACK_FOUND)
-#     find_path(LAPACKE_INCLUDE_DIR "lapacke.h")
-#     find_path(MKL_LAPACKE_INCLUDE_DIR "mkl_lapack.h")
-#     if(LAPACKE_INCLUDE_DIR)
-#       ocv_include_directories(${LAPACKE_INCLUDE_DIR})
-#       set(HAVE_LAPACK 1)
-#       set(HAVE_LAPACK_GENERIC 1)
-#     elseif(MKL_LAPACKE_INCLUDE_DIR)
-#       ocv_include_directories(${MKL_LAPACKE_INCLUDE_DIR})
-#       set(HAVE_LAPACK 1)
-#       set(HAVE_LAPACK_MKL 1)
-#     elseif(APPLE)
-#       set(HAVE_LAPACK 1)
-#       set(HAVE_LAPACK_APPLE 1)
-#     endif()
-#     list(APPEND OPENCV_LINKER_LIBS ${LAPACK_LIBRARIES})
-#   endif()
-# endif()
-
 # --- TBB ---
 if(WITH_TBB)
   include("${OpenCV_SOURCE_DIR}/cmake/OpenCVDetectTBB.cmake")

cmake/OpenCVFindMKL.cmake

@@ -7,10 +7,10 @@
 #
 # On return this will define:
 #
-# HAVE_MKL          - True if Intel IPP found
-# MKL_ROOT_DIR      - root of IPP installation
-# MKL_INCLUDE_DIRS  - IPP include folder
-# MKL_LIBRARIES     - IPP libraries that are used by OpenCV
+# HAVE_MKL          - True if Intel MKL found
+# MKL_ROOT_DIR      - root of MKL installation
+# MKL_INCLUDE_DIRS  - MKL include folder
+# MKL_LIBRARIES     - MKL libraries that are used by OpenCV
 #
 
 macro (mkl_find_lib VAR NAME DIRS)
@@ -21,7 +21,7 @@ endmacro()
 
 macro(mkl_fail)
     set(HAVE_MKL OFF)
-    set(MKL_ROOT_DIR ${MKL_ROOT_DIR} CACHE PATH "Path to MKL directory")
+    set(MKL_ROOT_DIR "${MKL_ROOT_DIR}" CACHE PATH "Path to MKL directory")
     return()
 endmacro()
 
@@ -46,11 +46,13 @@ if(NOT DEFINED MKL_USE_MULTITHREAD)
 endif()
 
 #check current MKL_ROOT_DIR
-if(NOT MKL_ROOT_DIR OR NOT EXISTS ${MKL_ROOT_DIR}/include/mkl.h)
-    set(mkl_root_paths ${MKL_ROOT_DIR})
+if(NOT MKL_ROOT_DIR OR NOT EXISTS "${MKL_ROOT_DIR}/include/mkl.h")
+    set(mkl_root_paths "${MKL_ROOT_DIR}")
     if(DEFINED ENV{MKLROOT})
-        list(APPEND mkl_root_paths $ENV{MKLROOT})
+        list(APPEND mkl_root_paths "$ENV{MKLROOT}")
     endif()
+
+    if(WITH_MKL AND NOT mkl_root_paths)
       if(WIN32)
         set(ProgramFilesx86 "ProgramFiles(x86)")
         list(APPEND mkl_root_paths $ENV{${ProgramFilesx86}}/IntelSWTools/compilers_and_libraries/windows/mkl)
@@ -58,11 +60,12 @@ if(NOT MKL_ROOT_DIR OR NOT EXISTS ${MKL_ROOT_DIR}/include/mkl.h)
       if(UNIX)
         list(APPEND mkl_root_paths "/opt/intel/mkl")
       endif()
+    endif()
 
     find_path(MKL_ROOT_DIR include/mkl.h PATHS ${mkl_root_paths})
 endif()
 
-set(MKL_INCLUDE_DIRS ${MKL_ROOT_DIR}/include CACHE PATH "Path to MKL include directory")
+set(MKL_INCLUDE_DIRS "${MKL_ROOT_DIR}/include" CACHE PATH "Path to MKL include directory")
 
 if(NOT MKL_ROOT_DIR
     OR NOT EXISTS "${MKL_ROOT_DIR}"
@@ -128,9 +131,9 @@ endforeach()
 
 message(STATUS "Found MKL ${MKL_VERSION_STR} at: ${MKL_ROOT_DIR}")
 set(HAVE_MKL ON)
-set(MKL_ROOT_DIR ${MKL_ROOT_DIR} CACHE PATH "Path to MKL directory")
-set(MKL_INCLUDE_DIRS ${MKL_INCLUDE_DIRS} CACHE PATH "Path to MKL include directory")
-set(MKL_LIBRARIES ${MKL_LIBRARIES} CACHE STRING "MKL libarries")
+set(MKL_ROOT_DIR "${MKL_ROOT_DIR}" CACHE PATH "Path to MKL directory")
+set(MKL_INCLUDE_DIRS "${MKL_INCLUDE_DIRS}" CACHE PATH "Path to MKL include directory")
+set(MKL_LIBRARIES "${MKL_LIBRARIES}" CACHE STRING "MKL libarries")
 if(UNIX AND NOT MKL_LIBRARIES_DONT_HACK)
     #it's ugly but helps to avoid cyclic lib problem
     set(MKL_LIBRARIES ${MKL_LIBRARIES} ${MKL_LIBRARIES} ${MKL_LIBRARIES} "-lpthread" "-lm" "-ldl")