Resolve build bot problems in unittests/Format/FormatTest.cpp

[bjope]

Summary

Make the new GetStyleWithEmptyFileName test case independent
of the file system used when running the test. Since the
test is supposed to use the fallback "Google" style we now
use a InMemoryFileSystem to make sure that we do not accidentaly
find a .clang-format file in the real file system. That could
for example happen when having the build directory inside the
llvm och clang repo (as there is a .clang-format file inside
the repos).

[bjope]

This is an attempt to fix problems seen after https://reviews.llvm.org/D43590

[benhamilton]

Thanks for fixing this. (Sorry for not getting to it, I was away traveling until today.)

I'll add a tidy-up in D43598 to ensure all tests which call getStyle() pass in an in-memory filesystem.

[benhamilton]

Actually, looks like all the other tests explicitly want a non-empty in-memory FS, so there's no good cleanup I can do.

[bjope]

In D43732#1020639, @benhamilton wrote:

Actually, looks like all the other tests explicitly want a non-empty in-memory FS, so there's no good cleanup I can do.

Well, it was only this new test case that failed, so I think other tests are fine (some of them have been adjusted in a similar way in the past if I remember correctly).
And our downstream integration bots has started to pull in things from trunk again, after I landed this fix.

unittests/Format/FormatTest.cpp

EXPECT_EQ("auto a = unique_ptr<Foo<Bar>[ 10 ]>;",
             format("auto a = unique_ptr < Foo < Bar>[10]> ;", Spaces));
 }
 
 TEST_F(FormatTest, NoSpaceAfterSuper) {
     verifyFormat("__super::FooBar();");
 }
 
 TEST(FormatStyle, GetStyleWithEmptyFileName) {
-  auto Style1 = getStyle("file", "", "Google");
+  vfs::InMemoryFileSystem FS;
+  auto Style1 = getStyle("file", "", "Google", "", &FS);
   ASSERT_TRUE((bool)Style1);
   ASSERT_EQ(*Style1, getGoogleStyle());
 }
 
 TEST(FormatStyle, GetStyleOfFile) {
   vfs::InMemoryFileSystem FS;
   // Test 1: format file in the same directory.
   ASSERT_TRUE(