PhysX SDK Releases <= 5.3.0 Packman errors when running generate_projects.bat|sh

[preist-nvidia]

When running generate_projects.bat|sh with PhysX SDK versions <= 5.3.0 there is an issue with older Packman versions failing to download dependencies. If you see errors as reported in #229, please do the following:

1. Navigate to physx/buildtools/packman
2. Run ./packman update -y

Now the projects generate will succeed. Apologies for this inconvenience.