How to devirtualize one class?

[Jeffrey Walton]

I'm catching a hang under Debian's ARM64 (AARCH64) in a QEMU Chroot.
The environment does not have a working debugger, so I have it roughly
isolated to two conditions.

I need to test -fno-devirtualize on a particular class (H and CPP
files), and I want to ensure it does not cross pollinate out of the
class. (Say, by, including the header in other header files).

How do I apply -fno-devirtualize to just the class when it needs to be
applied to a particular class's header file (and that header file is
included elsewhere) ?

Thanks in advance.