OSL v1.13.8.0

Release 1.13.8.0 -- 1 Apr 2024 (compared to 1.13.7.0)

• fix(batched): Codegen bug for compref with varying index for batched shading #1776 (by Alex Wells)
• fix: Calculatenormal needs fliphandedness #1783 (by sfriedmapixar)
• fix: Print closure missing error message at compile time instead of run time. #1781 (by sfriedmapixar)
• int: Change long-deprecated OIIO macro to new one #1788
• ci: Fix broken Macos-13 CI #1780