Enable in-package substitute of tr1/tuple

In clang 6.0 the tr1/tuple header is not present, and this cause a
compilation error inside of the gtest framework. However, if we set a
define, it will use its own substitute of tr1/tuple, which is sufficient
for the unit tests.

ApplicationCode/ReservoirDataModel/ReservoirDataModel_UnitTests/CMakeLists.txt

@@ -87,6 +87,8 @@ IF(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
         set(CMAKE_CXX_FLAGS_RELEASE "-O2 -DNO_DEBUG")
         set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ")
 
+ELSEIF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+        set(CMAKE_CXX_FLAGS         "-DGTEST_USE_OWN_TR1_TUPLE=1")
 ENDIF(${CMAKE_SYSTEM_NAME} MATCHES "Linux")