Clang physx builds in 4.23 seem to be broken due to a change of GuPersistentContactManifold.h including #pragma warning and no longer ending in a new line.
\Engine\Build\BatchFiles\RunUAT.bat BuildPhysX -TargetPlatforms=Linux -TargetConfigs=profile -TargetWindowsCompilers=VisualStudio2017 -SkipSubmit
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-83160 in the post.