Fix for CMake single threaded. #7609 (comment)

Author: dgarske

cmake/functions.cmake

@@ -251,7 +251,7 @@ function(generate_build_flags)
     endif()
     set(BUILD_EXAMPLE_CLIENTS ${WOLFSSL_EXAMPLES} PARENT_SCOPE)
     set(BUILD_TESTS ${WOLFSSL_EXAMPLES} PARENT_SCOPE)
-    if(NOT WOLFSSL_SINGLETHREADED AND WOLFSSL_EXAMPLES AND NOT WOLFSSL_LEAN_TLS)
+    if(NOT WOLFSSL_SINGLE_THREADED AND WOLFSSL_EXAMPLES AND NOT WOLFSSL_LEAN_TLS)
         set(BUILD_THREADED_EXAMPLES "yes" PARENT_SCOPE)
     endif()
     set(BUILD_WOLFCRYPT_TESTS ${WOLFSSL_CRYPT_TESTS} PARENT_SCOPE)