Fixed CMake variable reference

Author: ras0219-msft

Release/CMakeLists.txt

@@ -79,7 +79,7 @@ set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/Binaries)
 
 # These settings can be used by the test targets
 set(Casablanca_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/include)
-set(Casablanca_INCLUDE_DIRS ${CMAKE_CURRENT_SOURCE_DIR}/include ${Boost_INCLUDE_DIRS})
+set(Casablanca_INCLUDE_DIRS ${CMAKE_CURRENT_SOURCE_DIR}/include ${Boost_INCLUDE_DIR})
 set(Casablanca_LIBRARY ${LIB}casablanca)
 set(Casablanca_LIBRARIES ${Casablanca_LIBRARY} ${Boost_LIBRARIES} ${Boost_FRAMEWORK})