Ninja: Restore slash style for MinGW tools when extra languages are enabled

Since commit f3ca199c (cmGlobalNinjaGenerator: Factor out GNU-like
command-line detection on Windows, 2023-03-18, v3.26.1~2^2~6), we
accidentally "unrecognize" MinGW tools on Windows if a language other
than C or CXX is enabled.  This causes the wrong slash style to be
generated in paths in `build.ninja`.

Fixes: #24642