Merging r359496:

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r359496 | mstorsjo | 2019-04-29 13:25:51 -0700 (Mon, 29 Apr 2019) | 8 lines

[X86] Run CFIInstrInserter on Windows if Dwarf is used

This is necessary since SVN r330706, as tail merging can include
CFI instructions since then.

This fixes PR40322 and PR40012.

Differential Revision: https://reviews.llvm.org/D61252
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llvm-svn: 359952