crossbuild NetBSD on Linux fails

As recommended in the Developers Manual I modified GNUmakefile to:

DEFAULT_TARGET = netbsd
GDB_AUTOLOAD_PATH = /usr/pkg/share/gdb/auto-load

... and ran:

make clean
make

... which fails with:

1. &assertion &violation &serious
2. &who: assembler-library
3. &message: "Unsupported target"
4. &irritants: (amd64 netbsd) 

... which originates at the end of ./arch/asm.sls:(assembler-library) ... since targets seems to contain only 3 entries, but none for (amd64 netbsd):

(#[target cpu-id: amd64 kernel-id: pc+linux ...]
 #[target cpu-id: amd64 kernel-id: linux ...]
 #[target cpu-id: amd64 kernel-id: pc ] )

Why is that?

Btw: The code for "Self-cross-compilation for NetBSD/amd64" in ./.gitlab-ci.yml is commented out. Is this related?

Found with Loko release 0.12.2 in Manjaro-Linux x86_64 (VM).