[coff] use newlines instead of spaces as separators in msvclto response file

Summary:
Fixes PR32689: /msvclto creates response files with lines
that are too long for msvc's linker (LNK1170).

Reviewers: hans, rnk, ruiu

Subscribers: llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D32185

llvm-svn: 300612