fix echoBinSafe failure from #10559

[timotheecour]

• root cause of CI failure in system refactorings #10559 was tests/ccgbugs/twrongrefcounting.nim which uses -d:useGcAssert

indeed, gcAssert calls echo, which causes error: system module needs: echoBinSafe

Regardless of whether gcAssert should call echo or write(cstdout, ...), the problem is that we weren't able to use echo (or debugEcho) anywhere until after import io is called.

Not having access to echo makes it very inconvenient when we need to debug something inside system.nim (or its includes)

This PR fixes that.

[Araq]

Fixed it differently.