[libcxx] [test] Narrow down an XFAIL for clang-cl configurations

This test only fails on x86_64 clang-cl, not for i386.

(The root cause is still not explored, thus the FIXME is still
relevant.)

Differential Revision: https://reviews.llvm.org/D124994

Author: mstorsjo

libcxx/test/std/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/copy_move.pass.cpp

@@ -8,7 +8,7 @@
 
 // FIXME: In MSVC mode, even "std::function<int(int)> f(aref);" causes
 // allocations.
-// XFAIL: msvc && stdlib=libc++
+// XFAIL: target=x86_64-pc-windows-msvc && stdlib=libc++
 
 // <functional>