[OpenMP] Add missing weak definitions of missing variables (#77767)

Variables `__omp_rtl_assume_teams_oversubscription` and
`__omp_rtl_assume_threads_oversubscription `are used by functions:
`__kmpc_distribute_static_loop`, `__kmpc_distribute_for_static_loop `and
`__kmpc_for_static_loop`.

GitOrigin-RevId: 18798cf972cd0669d3b4b84da18d467542588802
3 files changed