Merging r369426 and r369443:

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r369426 | mstorsjo | 2019-08-20 20:58:05 +0200 (Tue, 20 Aug 2019) | 5 lines

[TargetMachine] Don't try to create COFFSTUB references on windows on non-COFF

This avoids spurious relocation types for windows/elf targets.

Differential Revision: https://reviews.llvm.org/D66401
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r369443 | mstorsjo | 2019-08-20 22:58:02 +0200 (Tue, 20 Aug 2019) | 11 lines

[test] Fix tests when run on windows after SVN r369426. NFC.

When running tests on windows, invoking "llc -march=<arch>" will
implicitly use windows as the target os, making these tests misbehave
after this change.

Fix the issue by using more specific -mtriple values instead of plain
-march in these tests.

This should hopefully fix buildbot failures like
http://lab.llvm.org:8011/builders/clang-x64-windows-msvc/builds/9816.
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llvm-svn: 369654