NetBSD/aarch64 has no libgcc or libstdc++. Drop arm64 tests.

llvm-svn: 215291
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 65760b4..b6274a8 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -6964,6 +6964,7 @@
   bool useLibgcc = true;
   if (Major >= 7 || (Major == 6 && Minor == 99 && Micro >= 49) || Major == 0) {
     switch(getToolChain().getArch()) {
+    case llvm::Triple::aarch64:
     case llvm::Triple::arm:
     case llvm::Triple::armeb:
     case llvm::Triple::thumb: