Resolve CMake warning, using an undefined variable. Don't attempt to use OSL_SHADER_DIR in it's own hint, introduced in fix for #73830. This was also overwriting the previous assignment from "OSL_COMPILER". Ref !136961
Resolve CMake warning, using an undefined variable. Don't attempt to use OSL_SHADER_DIR in it's own hint, introduced in fix for #73830. This was also overwriting the previous assignment from "OSL_COMPILER". Ref !136961