Export public functions implemented in assembly on Windows.
Export public functions implemented in assembly on Windows.

Summary:
By default, symbols aren't visible outside of the module that defines
them. To make them visible, they must be exported. The easiest way to do
that is to embed an `-export:symname` directive into the object file.

Reviewers: mstorsjo, rnk

Subscribers: christof, cfe-commits

Differential Revision: https://reviews.llvm.org/D51508

git-svn-id: 62ef012455b6b8fcec9c41ca270ebf409aae1006@341232 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libunwind,llvm-mirror/libunwind,llvm-mirror/libunwind