Windows build error with gdk-pixbuf and handling umlaut characters

While trying to build gst-plugins-good-1.0 on Windows with cerbero, two errors popped up. One is with building gdk-pixbuf and the other is with cerbero incorrectly handling umlaut characters printed by the gdk-pixbuf error.

The full build log: https://pastebin.com/2LJexESt which shows error in handling of the umlaut characters.

When opening the cerbero shell and running ninja, the following "real" build error is printed: https://pastebin.com/5fCkhzQE

I have checked that c:/gstreamer/cerbero/build/sources/windows_x86_64/gdk-pixbuf-2.38.0/tests/icc-profile.png exists and is a valid PNG file. (It is.)

The build.ninja file is attached: build.ninja