libsoup recipe looking for python in the wrong location on windows.

/usr/bin/env: python3: No such file or directory
make[2]: *** [soup-enum-types.c.stamp] Error 127
make[2]: Leaving directory `/c/code/cerbero/build/sources/msvc_x86_64/libsoup-2.60.3/libsoup'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/c/code/cerbero/build/sources/msvc_x86_64/libsoup-2.60.3'
make: *** [all] Error 2

This was doing a python ./cerbero-uninstalled -v visualstudio if that makes a difference. Worked around it by duplicating python.exe as python3.exe.