dmd build instructions from source don't work anymore

[John Colvin via Digitalmars-d]

On Monday, 11 May 2015 at 08:31:19 UTC, Timothee Cour wrote:
> git clone git://github.com/D-Programming-Language/dmd.git
> cd dmd
> make -f posix.mak MODEL=64
>
> /Applications/Xcode.app/Contents/Developer/usr/bin/make -C src 
> -f posix.mak
> no cpu specified, assuming X86
> dmd idgen.d
> g++ -m64: No such file or directory
> --- errorlevel 255
> make[1]: *** [idgen] Error 255
> make: *** [all] Error 2

Do you
1) already have a version of dmd installed (relatively new 
requirement)
and
2) have a working g++, whether of clang or gcc variety? On my 
machine g++ is in /usr/bin and is actually clang, although not as 
a symbolic link, as a slightly differently configured executable. 
Don't really know what apple's thinking here was.