Metal test suite rendering : image files are not found

[kwokcb]

Issue

I tried running Metal render tests and found that the image files are not found.
A comparison run using the same build does find image files.

Test output

Here is a snippet from the logged output run using `MaterialXTest "[rendermsl]"

Validating MSL rendering for: /Users/bernardkwok/work/bernard_materialx/build/bin/resources/Materials/Examples/StandardSurface/standard_surface_chess_set.mtlx
Image file not found: chess_set/king_white_base_color.jpg
Image file not found: chess_set/king_white_roughness.jpg
Image file not found: chess_set/king_white_normal.jpg
Validating MSL rendering for: /Users/bernardkwok/work/bernard_materialx/build/bin/resources/Materials/Examples/StandardSurface/standard_surface_chess_set.mtlx
Image file not found: chess_set/knight_black_base_color.jpg
Image file not found: chess_set/knight_black_roughness.jpg
Image file not found: chess_set/knight_black_normal.jpg

Example render comparison: