Following up to b555b8d.
Building Blender with hidden symbols but using libraries with visible symbols
was giving linker warnings, specifically for USD. So revert that for now, as
it was not needed for the bugfix.
Hide USD symbols (some of which are not in the USD namespace) to avoid potential
conflicts. May potentially help with AMD OpenCL issues in T74262.
This means symbols from Blender itself and most external libraries. We can't
just hide all because that breaks some libraries. The better solution would
be to rebuild all library dependencies with hidden visibility.
Fixes T75223: Luxrender add-on failing to load on macOS
