[MachO] Don't write test files to /tmp, remove them afterwards.

[mstorsjo]

Summary

This matches what is done in MachONormalizedFileBinaryWriterTests.cpp already.

[ruiu]

LGTM

unittests/MachOTests/MachONormalizedFileBinaryReaderTests.cpp

 //===- lld/unittest/MachOTests/MachONormalizedFileBinaryReaderTests.cpp ---===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "../../lib/ReaderWriter/MachO/MachONormalizedFile.h"
 #include "lld/ReaderWriter/MachOLinkingContext.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/Support/Error.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/YAMLTraits.h"
 #include "gtest/gtest.h"
 #include <cstdint>
 #include <memory>
 
+using llvm::SmallString;
 using llvm::StringRef;
 using llvm::MemoryBuffer;
+using llvm::Twine;
 
 using namespace lld::mach_o::normalized;
 using namespace llvm::MachO;
 
 static std::unique_ptr<NormalizedFile>
 fromBinary(const uint8_t bytes[], unsigned length, StringRef archStr) {
   StringRef sr((const char*)bytes, length);
   std::unique_ptr<MemoryBuffer> mb(MemoryBuffer::getMemBuffer(sr, "", false));
TEST(BinaryReaderTest, hello_obj_ppc) {
   EXPECT_EQ(mainLabel.scope, SymbolScope(N_EXT));
   EXPECT_EQ(mainLabel.value, Hex64(0x0));
   EXPECT_EQ(f->undefinedSymbols.size(), 1UL);
   const Symbol& printfLabel = f->undefinedSymbols[0];
   EXPECT_TRUE(printfLabel.name.equals("_printf"));
   EXPECT_EQ(printfLabel.type, N_UNDF);
   EXPECT_EQ(printfLabel.scope, SymbolScope(N_EXT));
 
-  auto ec = writeBinary(*f, "/tmp/foo.o");
-  // FIXME: We want to do EXPECT_FALSE(ec) but that fails on some Windows bots,
-  // probably due to /tmp not being available.
-  // For now just consume the error without checking it.
-  consumeError(std::move(ec));
+  SmallString<128> tmpFl;
+  std::error_code ec =
+      llvm::sys::fs::createTemporaryFile(Twine("xx"), "o", tmpFl);
+  EXPECT_FALSE(ec);
+  llvm::Error ec2 = writeBinary(*f, tmpFl);
+  EXPECT_FALSE(ec2);
+  llvm::sys::fs::remove(tmpFl);
 }