Fix tree/treeplayer/CMakeLists.txt

The header TProcessExecutor.hxx is from core/multiproc.
It was being removed before, so there was no problem if
didn't exist, but since the logic has been inverted to
add if needed, it created a problem.

tree/treeplayer/CMakeLists.txt

@@ -3,17 +3,15 @@
 # @author Pere Mato CERN, Danilo Piparo CERN
 ############################################################################
 
-if(imt)
+if(NOT MSVC)
   list(APPEND TREEPLAYER_EXTRA_HEADERS
-    ROOT/TTreeProcessorMT.hxx
+    TMPWorkerTree.h
+    ROOT/TTreeProcessorMP.hxx
   )
 endif()
 
-if(NOT MSVC)
+if(imt)
   list(APPEND TREEPLAYER_EXTRA_HEADERS
-    TMPWorkerTree.h
-    ROOT/TProcessExecutor.hxx
-    ROOT/TTreeProcessorMP.hxx
     ROOT/TTreeProcessorMT.hxx
   )
 endif()