FreeBSD: CXX Interop Voidify Tests

Disable Cxx tests failing on failed import of incorrectly imported
voidify symbol. This isn't just a FreeBSD issue, it's related to how we
import libcxx. Apple has a modified libcxx module to work around the
issue, but is not implemented in the copy on FreeBSD.

rdar://121551667

```
[2025-08-25T14:24:03.682Z] ld.lld: error: undefined hidden symbol: void* std::__1::__voidify[abi:se190107]<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>&)
[2025-08-25T14:24:03.682Z] >>> referenced by use-std-optional-a50ecf.o
[2025-08-25T14:24:03.682Z] >>>               /tmp/lit-tmp-_7a7wdmg/use-std-optional-a50ecf.o:(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>* std::__1::__construct_at[abi:se190107]<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>*>(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&))
[2025-08-25T14:24:03.682Z] >>> referenced by use-std-optional-a50ecf.o
[2025-08-25T14:24:03.682Z] >>>               /tmp/lit-tmp-_7a7wdmg/use-std-optional-a50ecf.o:(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>* std::__1::__construct_at[abi:se190107]<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>*>(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>&&))
[2025-08-25T14:24:03.682Z] clang: error: linker command failed with exit code 1 (use -v to see invocation)
[2025-08-25T14:24:03.682Z] <unknown>:0: error: link command failed with exit code 1 (use -v to see invocation)
```

Author: etcwilde

test/Interop/Cxx/stdlib/use-std-map.swift

@@ -13,6 +13,10 @@
 //
 // REQUIRES: OS=macosx || OS=linux-gnu || OS=freebsd
 
+// Undefined hidden symbol to C++ voidify in libcxx
+// rdar://121551667
+// XFAIL: OS=freebsd
+
 import StdlibUnittest
 #if !BRIDGING_HEADER
 import StdMap

test/Interop/Cxx/stdlib/use-std-optional.swift

@@ -5,6 +5,10 @@
 //
 // REQUIRES: executable_test
 
+// Undefined hidden symbol to C++ voidify in libcxx
+// rdar://121551667
+// XFAIL: OS=freebsd
+
 import StdlibUnittest
 import StdOptional
 import CxxStdlib