[libc++] Always build with -fvisibility=hidden

This avoids symbols being accidentally exported from the dylib when they
shouldn't. The next step is to use a pragma to apply hidden visibility
to all declarations (unless otherwise specified), which will allow us
to drop the per-declaration hidden visibility attributes we currently

This also has the nice side effect of making sure the dylib exports the
same symbols regardless of the optimization level.


Reviewers: EricWF, mclow.lists

Subscribers: mgorny, christof, jkorous, dexonsmith, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D62868

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@368703 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed