Blender Git Loki

Fix T93102: Principled hair shader stack was built incorrectly

stack_assign_if was used in the middle of creating the shader value blocks.
Which caused stack variables to be inserted in the middle of the shader value data.
This resulted in the shader node data no being in sequential order. This was also
the case for the wave texture wave node.

Reviewed By: brecht

Maniphest Tasks: T93102

Differential Revision: https://developer.blender.org/D13262