Merging r310990:

Merging r310990:
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r310990 | mstorsjo | 2017-08-15 22:18:36 -0700 (Tue, 15 Aug 2017) | 18 lines

[llvm-dlltool] Fix creating stdcall/fastcall import libraries for i386

Hook up the -k option (that in the original GNU dlltool removes the
@n suffix from the symbol that the final executable ends up linked to).

In llvm-dlltool, make sure that functions end up with the undecorate
name type if this option is set and they are decorated. In mingw, when
creating import libraries from def files instead of creating an import
library as a side effect of linking a DLL, the symbol names in the def
contain the stdcall/fastcall decoration (but no leading underscore).

By setting the undecorate name type, a linker linking to the import
library will omit the decoration from the DLL import entry.

With this in place, mingw-w64 for i386 built with llvm-dlltool/clang
produces import libraries that actually work.

Differential Revision: https://reviews.llvm.org/D36548
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_50@311408 91177308-0d34-0410-b5e6-96231b3b80d8