Fix example plugins build

[masaori335]

More fix of the log symbol issue. #10319

[jpeach]

I went down a bit of a rabbit hole on this one ....

IIUC this is a lllvm libc++ problem. <math.h> comes in via <atomic> which comes in via <DbgCtl.h>

.. ../../../include/ts/DbgCtl.h
... /usr/local/opt/llvm/bin/../include/c++/v1/atomic
.... /usr/local/opt/llvm/bin/../include/c++/v1/cstring
.... /usr/local/opt/llvm/bin/../include/c++/v1/cmath
..... /usr/local/opt/llvm/bin/../include/c++/v1/math.h

Relevant libc++ header says:

  #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
  #  include <cmath>
  #  include <compare>
  #  include <type_traits>
  #endif

So in theory, setting that define should help. However, if we do that, we end up with a different path:

... /usr/local/opt/llvm/bin/../include/c++/v1/utility
.... /usr/local/opt/llvm/bin/../include/c++/v1/compare
..... /usr/local/opt/llvm/bin/../include/c++/v1/__compare/compare_partial_order_fallback.h
...... /usr/local/opt/llvm/bin/../include/c++/v1/__compare/partial_order.h
....... /usr/local/opt/llvm/bin/../include/c++/v1/__compare/compare_three_way.h
....... /usr/local/opt/llvm/bin/../include/c++/v1/__compare/weak_order.h
........ /usr/local/opt/llvm/bin/../include/c++/v1/__compare/strong_order.h
......... /usr/local/opt/llvm/bin/../include/c++/v1/cmath
.......... /usr/local/opt/llvm/bin/../include/c++/v1/math.h

And in <cmath> we find code like this, which unconditionally pulls <math.h> into the global namespace:

...
#include <math.h>
...
_LIBCPP_BEGIN_NAMESPACE_STD
...
_LIBCPP_END_NAMESPACE_STD
...

So yeh, c++ seems like it's a bug mess with regard to <math.h> symbols.