...as a consequence of <https://gerrit.libreoffice.org/#/c/60375/> "Support for
building with macOS SDK < 10.12 is long gone"

Change-Id: Ic87a9608b4defbeb5cf066d61f6819226dd58c1b
Reviewed-on: https://gerrit.libreoffice.org/60377
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>