Reference model changes for fp16 support

Change-Id: I72f21fcfa153046274969d327313e3349981dbe6
Signed-off-by: James Ward <james.ward@arm.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d3281c6..6556b27 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,6 +12,7 @@
 option(SERIALIZATION_DIR "Location where the TOSA Serialization Library 'include' folder is found" Off)
 option(FLATBUFFERS_DIR "Location where the FlatBuffers 'include' and 'lib' folders is found" Off)
 option(EIGEN_DIR "Location where the Eigen folder is found" Off)
+option(HALF_DIR "Location where the Half folder is found" Off)
 option(DOCTEST_DIR "Location where the doctest folder is found (If building unit tests)" Off)
 
 add_subdirectory(thirdparty)