fixes strictdefs with when nimvm

[ringabout]

ref #24225
related #24306

Code in branches must not affect semantics of the code that follows the
when nimvm statement. E.g. it must not define symbols that are used in
the following code.

The test shouldn't have passed when #24306
would be implemented somehow. Some third packages have already misused when nimvm by defining symbols in the other branch of when nimvm.

e.g. in status-im/nim-unittest2#34

when nimvm:
  discard
else:
  let suiteName {.inject.} = nameParam

use(suiteName)

[github-actions]

Thanks for your hard work on this PR!
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