graphics/openshadinglanguage: return accidentally deleted USES=llvm:lib

PR: 279846
Reported by: fluffy (via IRC)
Fixes: cfcb40e24056 (update 1.12.14.0 → 1.13.10.0)
MFH: 2024Q3

(cherry picked from commit 38034248fe1b1dbd5fe4ff687b71b646612e9140)