When using the tracy ON_DEMAND mode, it is ok in most cases to drop measurements and do a GPU clock synchronization (that may stall) during the first tracyCollect. This is not enabled by default in the CMakeLists for backward compatibility and because it may be a bit intrusive.
This commit also makes the OpenGL tracy TracyGpuZone* a tiny bit more efficient by not calling the threadlocal GetGpuCtx(). It is also more resilient if no context has been declared on this thread. This means that the application will not crash if a context was used on different threads even though declared only on one (thus GetGpuCtx().ptr == nullptr). Tracy does not support this scenario, so on one hand this helps users by not crashing, on the other it is an error that is now silent.
This usually prevents the compiler from emitting warnings about stuff it found in
the included files.
Since the CMakeLists.txt seems to be exclusively meant for code that is making use
of Tracy rather than Tracy itself using it to build, silencing the warnings should probably
be what most folks would want.
This will prevent things like #126
