Using "make install" target seems to not install some of the header
files. I've run into missing ell/useful.h for recent iwd build from git
master.

Can you clarify whether all these header files should be installed when
building a distribution package and please make the Makefile install
those that are expected to be present on the system.

cp ell/*.h "$pkgdir"/usr/include/ell/ shows these additional files now:

/usr/include/ell/asn1-private.h
/usr/include/ell/cert-private.h
/usr/include/ell/dbus-private.h
/usr/include/ell/dhcp-private.h
/usr/include/ell/dhcp6-private.h
/usr/include/ell/ecc-private.h
/usr/include/ell/gvariant-private.h
/usr/include/ell/icmp6-private.h
/usr/include/ell/main-private.h
/usr/include/ell/missing.h
/usr/include/ell/net-private.h
/usr/include/ell/netlink-private.h
/usr/include/ell/pem-private.h
/usr/include/ell/private.h
/usr/include/ell/rtnl-private.h
/usr/include/ell/siphash-private.h
/usr/include/ell/time-private.h
/usr/include/ell/tls-private.h
 usr/include/ell/useful.h

-Andy
Arch Linux