If I take a look at the pkg build server of aarch64 things are broken.
- head-arm64-default is already broken for a couple of weeks, because it can't build 'pkg' 
- 113arm64-quarterly stays in 'parallel_build' while all cpu's are idle.
Is there maintenance being done? Where should I report this?
NB: I can't select "Package Infrastructure" as component.
 Log ends in:
install -m 0644 /wrkdirs/usr/ports/ports-mgmt/pkg/work/pkg-1.13.2/NEWS /wrkdirs/usr/ports/ports-mgmt/pkg/work/stage/usr/local/share/doc/pkg/NEWS
====> Compressing man pages (compress-man)
Bad system call
Aarch64 pkgs for 113-quarterly and 121-quarterly are building again. Thanks for fixing! 
The head-latest build is still failing on building 'ports-mgmt/pkg' because of a "Bad system call" . I guess the host kernel needs an upgrade.
Head-latest is broken since January, 13th.
The pkg repository is updated!
On http://pkg.freebsd.org/FreeBSD:13:aarch64/ the directory date changed.
latest/ 2020-Jan-04 12:39
latest/ 2020-May-16 06:24
And http://thunderx1.nyi.freebsd.org/ shows happy compile runs again.
Case closed. Thanks anonymous somebody for fixing this.