Compile Phobos library ?

[GG]

Hello !
I have already used gdb to debug program compiled with dmd, but never link gdb with DMD at same time.
I found on google something like this : nameofprogram -g -d gdb
But when I try with DMD like : DMD -g -d gdb [...] , the compiler DMD look for a .d file (cannot read file gdb.d) Of course, it's normal.
So could you explain me how to link gdb with DMD ? Is there an option parameter to pass to DMD?

Thanks !
GG