D tools build problem

[Joseph Rushton Wakeling]

Hello all,

I've started encountering a problem recently when building the D tools (i.e. 
rdmd et al.).

$ make -f posix.mak
../dmd/src/dmd -m64  -ofgenerated/linux/64/rdmd rdmd.d
Error: cannot find source code for runtime library file 'object.d'
        dmd might not be correctly installed. Run 'dmd -man' for installation 
instructions.
Specify path to file 'object.d' with -I switch
make: *** [generated/linux/64/rdmd] Error 1

I take it the error is because the makefile tries to build using ../dmd/src/dmd 
(which exists, I've built it) but can't find the corresponding runtime files.

There's an easy workaround -- use

     make -f posix.mak DMD=/opt/bin/dmd

(i.e. using the just-installed-2-minutes-before dmd), but it's annoying.  Is 
this a known issue?  Is there something I need to change about my build setup 
that I've missed?

Thanks & best wishes,

     -- Joe