Propagate CMake dependency for opengl/x11

[qbisi]

Hi, this pr aims to fix cmake configure error of vtk-9.6.0 when building with openusd with materialx.
In nixpkgs, the cmake configure system will complain

CMake Error at /nix/store/0b2sw8gp8qa0pqznnhirlm2gqx8h919b-python3.13-materialx-1.39.4/lib/cmake/MaterialX/MaterialXTargets.cmake:270 (set_target_properties):
  The link interface of target "MaterialXRenderHw" contains:

    X11::X11

  but the target was not found.  Possible reasons include:

    * There is a typo in the target name.
    * A find_package call is missing for an IMPORTED target.
    * An ALIAS target is missing.

also the target OpenGL::OpenGL X11::Xt is required to link with other MaterialX target.

So, i believe MaterialX need to propagate dependency OpenGL/libX11/libXt for downstream project to link with.

Note, in the last commit, i propagate OpenGL dependency conditionally as only the target MaterialXRenderGlsl link publicly with OpenGL, so i propagate OpenaGl optionally when downstream project require the component RenderGlsl explicitly (e.g. openusd might need this), tell me if you want this to be unconditionally propagated.

resolve #2421.
cc @spiffmon

[linux-foundation-easycla]

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• ✅ login: qbisi / name: qbisicwate (3a30d52, d798775, dbecc39)

[jstone-lucasfilm]

This looks very promising, thanks @qbisi, and I'd love to get feedback from @spiffmon, @JGamache-autodesk, and other domain experts before merging it.

[qbisi]

Thanks for quick responding, updated the last commit (find opengl should be in scope unix and not macos).

[JGamache-autodesk]

LGTM!

[jstone-lucasfilm]

Thanks for putting this together, @qbisi!

[qbisi]

Hi, any plan to make a new release in 2026. I would like to make a pr to downstream openusd that make use of the finding MaterialXRenderHw component.

[jstone-lucasfilm]

@qbisi Yes, we're in the process of organizing a MaterialX v1.39.5 release, and we'll send out announcements once the first release candidate is available.