[LLD] [COFF] Add a missing REQUIRES line to a recently added test. NFC.

This should fix failing buildbots like
http://lab.llvm.org:8011/builders/clang-cmake-aarch64-lld/builds/7180.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@370491 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/COFF/mixed-resource-obj.yaml b/test/COFF/mixed-resource-obj.yaml
index 60f0ebe..8e122b5 100644
--- a/test/COFF/mixed-resource-obj.yaml
+++ b/test/COFF/mixed-resource-obj.yaml
@@ -1,3 +1,5 @@
+# REQUIRES: x86
+
 # RUN: yaml2obj < %s > %t.o
 
 # Test that we get both the resource and the code from a single object