Storm MaterialX 'edf' shader compilation error on Metal

[pablode]

Description of Issue

This is an isolated bug report for the issue mentioned in #2479.

The scene VeachAjar.zip throws multiple error messages and renders incorrectly with Storm's metal backend:

Warning: in _ValidateCompilation at line 229 of /Users/pablode/USD/pxr/imaging/hdSt/glslProgram.cpp -- Failed to compile shader (FRAGMENT_SHADER): program_source:2600:5: error: unknown type name 'EDF'
    EDF edf;
    ^

Steps to Reproduce

1. open the attached file with usdview on macOS

System Information (OS, Hardware)

MacBook Air M3, Sonoma 14.4.1

Package Versions

v24.05

Build Flags

--openimageio --opencolorio

[jesschimein]

Filed as internal issue #USD-9566