[libc] Fix global constructor being emitted for the RPC client

The indirection here is for some reason causing an unnecessary
constructor. If we leave this uninitialized we will get the default
constructor which simply zero initliaizes the global. I've checked the
output and confirmed that it uses the `zeroinitializer` so this should
be safe.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D155720