cross compile for rpi3 help needed

[Per olof Ljungmark]

In the process of learning arm I have set up a testing platform with
12-CURRENT r336739 and reading release(7).

The only change made to src is
SRCBRANCH="base/head at r337160"
in RPI3.conf

/etc/make.conf and src.conf are empty

command is

sh release.sh -c arm64/RPI3.conf

The build goes on for a while and stops with
...
--- installconfig_subdir_usr.bin/ofed/libibverbs/ud_pingpong ---
===> usr.bin/ofed/libibverbs/ud_pingpong (installconfig)
--- installconfig_subdir_share ---
--- installconfig_subdir_share/vt ---
===> share/vt (installconfig)
--- installconfig_subdir_share/zoneinfo ---
===> share/zoneinfo (installconfig)
--- installconfig_subdir_share/vt ---
--- installconfig_subdir_share/vt/fonts ---
===> share/vt/fonts (installconfig)
--- installconfig_subdir_share/vt/keymaps ---
===> share/vt/keymaps (installconfig)
chroot: /etc/rc.d/ldconfig: Exec format error

What am I missing here?