Add missing XFAIL to libcxx/test/std/strings/basic.string/string.capacity/over_max_size.pass.cpp

Author: ldionne

libcxx/test/std/strings/basic.string/string.capacity/over_max_size.pass.cpp

@@ -8,6 +8,12 @@
 
 // UNSUPPORTED: no-exceptions
 
+// After changing the alignment of the allocated pointer from 16 to 8, the exception
+// thrown is no longer `bad_alloc` but instead length_error on systems using new
+// headers but a dylib that doesn't contain 04ce0ba.
+//
+// XFAIL: using-built-library-before-llvm-19
+
 // <string>
 
 // size_type max_size() const; // constexpr since C++20