[NFC] Fix for InterfaceStubs tests (adding REQUIRES: x86-registered-target).

clang-hexagon-elf bot was failing with:

'No available targets are compatible with triple "x86_64-unknown-linux-gnu"'

Adding a "// REQUIRES: x86-registered-target" to these tests to quiet the bot.

llvm-svn: 363963
diff --git a/clang/test/InterfaceStubs/visibility.cpp b/clang/test/InterfaceStubs/visibility.cpp
index 87ea7ea..137c593 100644
--- a/clang/test/InterfaceStubs/visibility.cpp
+++ b/clang/test/InterfaceStubs/visibility.cpp
@@ -1,3 +1,4 @@
+// REQUIRES: x86-registered-target
 // RUN: %clang -target x86_64-unknown-linux-gnu -o - -emit-interface-stubs \
 // RUN: -interface-stub-version=experimental-tapi-elf-v1 -fvisibility=hidden \
 // RUN: %s | FileCheck --check-prefix=CHECK-CMD-HIDDEN %s