[libcxx] Preserve order, avoid duplicates when merging static archives

glob can return files in arbitrary order which breaks deterministic
builds. Rather, use `ar t` to list the files in each archive and
preserve the original order. Using `ar q` results in duplicate entries
in the archive, instead use `ar r` to avoid duplicates.

Differential Revision: https://reviews.llvm.org/D58024

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@353671 91177308-0d34-0410-b5e6-96231b3b80d8