Fix FindTBB version detection with TBB >= 2021.1.1

- Raised as issue #669

Change-Id: Ic2fcaf31aef5e303d19a9caef7d6c679325f554a

cmake/FindTBB.cmake

diff --git a/cmake/FindTBB.cmake b/cmake/FindTBB.cmake
index 5ae7b61..10e540d 100644
--- a/cmake/FindTBB.cmake
+++ b/cmake/FindTBB.cmake
@@ -429,10 +429,23 @@
 #=============================================================================
 #parse all the version numbers from tbb
 if(NOT TBB_VERSION)
+  set(TBB_VERSION_FILE_PRIOR_TO_TBB_2021_1
+    "${TBB_INCLUDE_DIR}/tbb/tbb_stddef.h")
+  set(TBB_VERSION_FILE_AFTER_TBB_2021_1
+    "${TBB_INCLUDE_DIR}/oneapi/tbb/version.h")
+
+  if (EXISTS "${TBB_VERSION_FILE_PRIOR_TO_TBB_2021_1}")
+    set(TBB_VERSION_FILE "${TBB_VERSION_FILE_PRIOR_TO_TBB_2021_1}")
+  elseif (EXISTS "${TBB_VERSION_FILE_AFTER_TBB_2021_1}")
+    set(TBB_VERSION_FILE "${TBB_VERSION_FILE_AFTER_TBB_2021_1}")
+  else()
+    message(FATAL_ERROR "Found TBB installation: ${TBB_INCLUDE_DIR} "
+      "missing version header.")
+  endif()
 
  #only read the start of the file
  file(STRINGS
-      "${TBB_INCLUDE_DIR}/tbb/tbb_stddef.h"
+      "${TBB_VERSION_FILE}"
       TBB_VERSION_CONTENTS
       REGEX "VERSION")