Refine the download of TBB

external_libs/CMakeLists.txt

@@ -12,11 +12,15 @@ endif (NOT (EXISTS ${CPM_DOWNLOAD_LOCATION}))
 
 include (${CPM_DOWNLOAD_LOCATION})
 
+if (TBB_DIR)
+	unset (TBB_DIR CACHE)
+endif ()
+
 CPMAddPackage (
 	NAME tbb
 	GITHUB_REPOSITORY oneapi-src/oneTBB
 	GIT_TAG v2021.3.0
-	OPTIONS "TBB_TEST OFF" "TBBMALLOC_BUILD OFF"
+	OPTIONS "TBB_TEST OFF" "TBBMALLOC_BUILD OFF" "TBB_FIND_PACKAGE OFF"
 )
 
 if (tbb_ADDED)