[Issue 20822] when building dmd, control characters for the console are included even when the host DC is piped

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20822

--- Comment #1 from Basile-z <b2.temp at gmx.com> ---
confirmed even when forcing no color, e.g

  $ export DFLAGS="-color=off" && ./build.d > a.out

then the error message contains control characters.

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