Windows Msys terminal not flushing on newlines

[kdevel]

Don't know if this is OT here.

On Sunday, 27 March 2022 at 18:09:30 UTC, Adam D Ruppe wrote:
> If the C library thinks it is talking to a pipe, it will switch 
> to block buffering instead of line buffering. It must just 
> think msys is a pipe (since it probably is under the hood).

while compiling a project with make -j6 I see this:

[...]
decimal/decimal.d(13080): decimal/decimal.d(13080): Deprecation: 
Deprecation: UUssagea goef  otfh et h`e `bodbyody` k`e ykweoyrwdo 
rids  idse pdreepcraetceadt.e dU.s eU s`e `dodo` i`n sitnesatde.a
d.
decimal/decimal.d(13217): decimal/decimal.d(13217): Deprecation: 
Deprecation: UUssaaggee  ooff  tthhee  ``bbooddyy``  
kkeeyywwoorrdd  iiss  ddeepprreeccaatteedd..  UUssee  ``ddoo``  
iinnsstteeaadd..

decimal/decimal.d(13239): Deprecation: decimal/decimal.d(13239): 
UDeprecation: sageU soafg et hoef  `the b`odybo`d ykey`w okredy 
wiosr dd eipsr edceaptreedc.a tUesde.  `Use d`o`d oins`t eiands.t
ead.
decimal/decimal.d(13327): decimal/decimal.d(13327): Deprecation: 
Deprecation: UUssaaggee  ooff  tthhee  ``bbooddyy``  
kkeeyywwoorrdd  iiss  ddeepprreeccaatteedd..  UUssee  ``ddoo``  
iinnsstteeaadd..

The write calls are mostly unbuffered as strace reveals:

29680 write(2, "\33[1m", 4)             = 4
29680 write(2, "decimal/decimal.d(471): ", 24) = 24
29680 write(2, "\33[1;36m", 7)          = 7
29680 write(2, "Deprecation: ", 13)     = 13
29680 write(2, "\33[m", 3)              = 3
29680 write(2, "U", 1)                  = 1
29680 write(2, "s", 1)                  = 1
29680 write(2, "a", 1)                  = 1
29680 write(2, "g", 1)                  = 1
29680 write(2, "e", 1)                  = 1
29680 write(2, " ", 1)                  = 1
29680 write(2, "o", 1)                  = 1
29680 write(2, "f", 1)                  = 1
29680 write(2, " ", 1)                  = 1
29680 write(2, "t", 1)                  = 1
29680 write(2, "h", 1)                  = 1
29680 write(2, "e", 1)                  = 1
29680 write(2, " ", 1)                  = 1

> Normally the IOLBF thing does help there - that means line 
> buffering - but my recommentation is to explicitly call 
> `stdout.flush()` any time it is important in your code. Then 
> you aren't depending on the relatively hidden config value.

Shall I file an issue for this?