make vs-ide-integration bumbling on paths in Windows

[Ilmari Lauhakangas]

A Windows user gets this when running make vs-ide-integration:

D:/libre/lode/opt/bin/make -j 4 -rs -f 
D:/libre/lode/dev/core/Makefile.gbuild gbuildtojson
cd D:/libre/lode/dev/core &&  D:/libre/lode/dev/core/bin/gbuild-to-ide 
--ide vs --make D:/libre/lode/opt/bin/make
python3: can't open file 
'/cygdrive/d/libre/lode/dev/core/D:/libre/lode/dev/core/bin/gbuild-to-ide': 
[Errno 2] No such file or directory
make: *** [Makefile:495: vs-ide-integration] Error 2

What can make Python think the gbuild-to-ide resides in such a curious path?

Ilmari