[PATCH] tools build: Fix clang detection with clang >= 8.0

[Matthew Dawson <matthew@mjdsystems.ca>]

The 8.0 release of clang/llvm moved the VirtualFileSystem.h header
to from clang to llvm.  This change causes a compile error, causing
perf to not detect clang/llvm.

Fix by including the right header for the different versions of llvm,
using the older header for llvm < 8, and the new header for llvm >= 8.

Signed-off-by: Matthew Dawson <matthew@mjdsystems.ca>
---
 tools/build/feature/test-clang.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/build/feature/test-clang.cpp b/tools/build/feature/test-clang.cpp
index a2b3f092d2f0..313ef1568880 100644
--- a/tools/build/feature/test-clang.cpp
+++ b/tools/build/feature/test-clang.cpp
@@ -1,10 +1,14 @@
 // SPDX-License-Identifier: GPL-2.0
-#include "clang/Basic/VirtualFileSystem.h"
 #include "clang/Driver/Driver.h"
 #include "clang/Frontend/TextDiagnosticPrinter.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/raw_ostream.h"
+#if LLVM_VERSION_MAJOR >= 8
+#include "llvm/Support/VirtualFileSystem.h"
+#else
+#include "clang/Basic/VirtualFileSystem.h"
+#endif
 
 using namespace clang;
 using namespace clang::driver;
-- 
2.21.0