rts: Fix reference to NUMA-specific field
rts: Fix reference to NUMA-specific field

This snuck into c51caafae7669d4246f4efd3d1a6858020780e02.

GaloisInc/halvm-ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc