/usr/share/debmake/extra0override/multiarch is in debmake 4.2.9-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | ### Multiarch package requires library files to be installed to
### /usr/lib/<triplet>/ . If the build system does not support
### $(DEB_HOST_MULTIARCH), you may need to override some targets such as
### dh_auto_configure or dh_auto_install to use $(DEB_HOST_MULTIARCH) .
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