In commit 9a0d5a82 (Ninja: add /DEF: flag to linker call, 2012-03-10,
v2.8.8~22^2~7) the logic should have been added to `GetTargetFlags` in
place of the older logic in that method from commit 7cef36c6 (ENH: add
the ability to generate custom commands for a language that is not
supported by an IDE, 2004-10-21, v2.4.0~2655).

Fixes: #23570