Could we add a new startup option to turn `ALWAYS_COPY_STACKS` on/off at runtime?

[KDr2]

I notice that we had done many things about the COPY_STACKS, mostly at the PRs #13099 and #29578.

Now by default, COPY_STACKS is enabled and ALWAYS_COPY_STACKS is disabled. But for some reasons, I need the option ALWAYS_COPY_STACKS to be enabled. For now, I have to download the source, define the macro in options.h and compile Julia by myself rather than just downloading a prebuilt tar-ball from the Julia website.

So I am considering is it apposite to add a new startup argument to switch this option — just for ALWAYS_COPY_STACKS when COPY_STACKS is enabled, not for COPY_STACKS, COPY_STACKS is still determined during the compiling time. So it is easy to do this.

Maybe we can do it in the way in which java does that kind of things, add a non-standard command line option(-X...)?