Edit /etc/dmd.conf to point the runtime library. The runtime library is found in src directory. My dmd.conf looks like
[Environment] ;dflags=...@p%/../src/phobos -...@p%/../src/druntime/import -l...@p%/../lib DFLAGS=-I/usr/local/dmd/src/phobos -I/usr/local/dmd/src/druntime/import -L-L/usr/local/dmd/lib
