[PDB] Error on too large stream directories

We hit this in Chromium builds where the PDB file was just under 4GB,
but the stream directory was actually too large to be correctly
represented.

llvm-pdbutil would error about this in llvm::msf::validateSuperBlock,
but lld should not write such PDB files in the first place.

Differential revision: https://reviews.llvm.org/D144385