/usr/src/glibc/debian/sysdeps/arm64.mk is in eglibc-source 2.19-0ubuntu6.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | libc_add-ons = ports nptl $(add-ons)
extra_config_options = --enable-multi-arch
|