Remove Metashade override-first library loading from MaterialXTest

[ppenenko]

Summary

Reverts the C++ MaterialXTest changes that were made to support Metashade override-first library loading. With PR #12 merged, the override loading is now handled entirely by the Python test infrastructure (test_render_metashade.py).

Provenance

These changes effectively revert the library-path-related portions of the following PRs and commits:

PR / Commit	Title	What's reverted
PR #5	Schlick BSDF override verification with Metashade wrapper	Override-first library loading, source code search path registration, extraLibraryPaths value
041705a8	Relative path to extra libraries	extraLibraryPaths value in _options.mtlx
35ef81cc	WIP: Override-first library loading for Metashade implementation priority	Load order reversal + source path registration in RenderUtil.cpp
34afa787	Revert "Remove registration of source code search paths..."	Re-added source path registration in initializeGeneratorContext
PR #9	Move metashade submodule to contrib and update path configurations	Updated extraLibraryPaths path (only the path portion is reverted)

Changes

resources/Materials/TestSuite/_options.mtlx

• Clear extraLibraryPaths back to "" (matching ASWF upstream)

source/MaterialXTest/MaterialXRender/RenderUtil.cpp

loadDependentLibraries — Restore stdlib-first load order:

• Was: extra libs loaded before stdlib for override priority via document insertion order
• Now: stdlib loaded first, then extra libs (matching ASWF upstream behavior)

initializeGeneratorContext — Remove extra source code search path registration:

• Removed: loop registering extraLibraryPaths as source code search paths
• Removed: registration of libraries/pbrlib/genglsl for wrapper GLSL #include resolution

Why

1. No longer needed — Python tests handle override loading via explicit mx.readFromXmlFile() with priority ordering
2. Undesirable — the C++ mechanism caused the Metashade override to load unconditionally in all C++ render tests

Not changed

framesPerMaterial, envSampleCount, GPU timer infrastructure, and enableTracing options are intentionally preserved — these are separate profiling features from PR #1469 (autodesk-forks PRs AcademySoftwareFoundation#2821, AcademySoftwareFoundation#2822, AcademySoftwareFoundation#2824) with open upstream PRs.

[Copilot]

Pull request overview

This PR reverts prior C++ test-harness changes in MaterialXTest that enforced Metashade “override-first” library loading, returning behavior to the upstream (stdlib-first) load order and removing extra shader source search-path registration. The goal is to ensure Metashade overrides are applied only where explicitly intended (now handled by the Python test infrastructure), rather than affecting all C++ render tests.

Changes:

• Restore standard-library-first dependency load order in ShaderRenderTester::loadDependentLibraries.
• Remove registration of extraLibraryPaths and libraries/pbrlib/genglsl as shader source code search paths in initializeGeneratorContext.
• Clear the default extraLibraryPaths test option back to an empty string in _options.mtlx.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
source/MaterialXTest/MaterialXRender/RenderUtil.cpp	Reverts override-first dependent library loading and removes extra source code search path registrations.
resources/Materials/TestSuite/_options.mtlx	Resets extraLibraryPaths to empty to match upstream defaults and avoid unconditional Metashade overrides in C++ tests.

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