cmake: fix LAPACK/MKL detection

cmake/OpenCVFindLAPACK.cmake

@@ -121,23 +121,22 @@ if(WITH_LAPACK)
         set(LAPACK_IMPL         "LAPACK/MKL")
         ocv_lapack_check()
       endif()
-      if(LAPACKE_INCLUDE_DIR AND NOT HAVE_LAPACK)
-        set(LAPACK_INCLUDE_DIR  ${LAPACKE_INCLUDE_DIR})
-        set(LAPACK_CBLAS_H      "cblas.h")
-        set(LAPACK_LAPACKE_H    "lapacke.h")
-        set(LAPACK_IMPL         "LAPACK/Generic")
-        ocv_lapack_check()
-      elseif(APPLE)
-        set(LAPACK_CBLAS_H      "Accelerate/Accelerate.h")
-        set(LAPACK_LAPACKE_H    "Accelerate/Accelerate.h")
-        set(LAPACK_IMPL         "LAPACK/Apple")
-        ocv_lapack_check()
-      else()
-        unset(LAPACK_LIBRARIES)
-        unset(LAPACK_LIBRARIES CACHE)
+      if(NOT HAVE_LAPACK)
+        if(LAPACKE_INCLUDE_DIR)
+          set(LAPACK_INCLUDE_DIR  ${LAPACKE_INCLUDE_DIR})
+          set(LAPACK_CBLAS_H      "cblas.h")
+          set(LAPACK_LAPACKE_H    "lapacke.h")
+          set(LAPACK_IMPL         "LAPACK/Generic")
+          ocv_lapack_check()
+        elseif(APPLE)
+          set(LAPACK_CBLAS_H      "Accelerate/Accelerate.h")
+          set(LAPACK_LAPACKE_H    "Accelerate/Accelerate.h")
+          set(LAPACK_IMPL         "LAPACK/Apple")
+          ocv_lapack_check()
+        endif()
       endif()
-    else()
-      # LAPACK not found
+    endif()
+    if(NOT HAVE_LAPACK)
       unset(LAPACK_LIBRARIES)
       unset(LAPACK_LIBRARIES CACHE)
     endif()