Set --run args only when we're actually running

[Simn]

This changes the behavior of Sys.args() to what @tobil4sk suggests in #11087 (comment).

Doesn't add a test yet because our sys tests require a PHD.

[Simn]

Also, the fact that this doesn't cause any sys test failures is probably concerning...

Edit: Actually it looks like these tests exclusively check --run, so it's expected to not break anything there. In that case all we really need to test is that macros don't have the runtime args on any target.

[tobil4sk]

In that case all we really need to test is that macros don't have the runtime args on any target.

Note, the only possible target where runtime args can be available at macro time is eval, because it is always compiled and run together. For other targets, compilation and execution are completely separate, so there is no way the macro could know what cli arguments the generated code will be run with.

Maybe this would make more sense as an eval-specific test.

[Simn]

I was thinking of some crazy case where we would leak com.args from --run to the macro context, but yeah, that doesn't seem like it would be possible.

[tobil4sk]

Maybe worth adding a test for --interp as well, so we know the compiler flags don't bleed through into runtime.