BUILD-Windows.txt says the following, but does not say in which files to uncomment these lines:
Finally, you need to manually uncomment the following two lines:
//#define IDXTYPEWIDTH 32
//#define REALTYPEWIDTH 32
To compile METIS with 64 bit integers or 64 bit floats, you also need
to set IDXTYPEWIDTH or REALTYPEWIDTH to 64.