CMake errors building LVL

[TonyBarbour]

There are CMake errors that result from CMake looking for pthread_create and secure_getenv in build/CMakeFiles/CMakeError.log. While these don't prevent anything from building, when things do go wrong they are sometimes a distraction from the real issue. We have had them reported in multiple issues, most recently in VulkanSamples, as the cause of compile failures, when the real cause was something else.

[TonyBarbour]

Logfile from building today's master. CMakeError.log

[TonyBarbour]

Closed as Vulkan-Loader #10