The command:

/Users/walter/dmd.2.096.1/osx/bin/dmd build.d

run in the dmd/src directory produces:

Warning: Syncing file access because of OSX!
Undefined symbols for architecture x86_64:
  "__D3std6format15FormatException6__ctorMFNaNbNfAyaQdmC6object9ThrowableZCQCrQCqQCm", referenced from:
      __D3std6format__T14formattedWriteTSQBg5stdio4File17LockingTextWriterTaTAyaZQCgFNfKQBwIAaQrZk in build.o
      __D3std9exception__T7bailOutHTCQBc6format15FormatExceptionZQBnFNaNfAyamMAxaZv in build.o
      __D3std6format__T6getNthVAyaa13_696e7465676572207769647468SQCe6traits10isIntegralTiTQChZQCtFNaNfkQCuZi in build.o
      __D3std6format__T6getNthVAyaa17_696e746567657220707265636973696f6eSQCm6traits10isIntegralTiTQCpZQDbFNaNfkQDcZi in build.o
      __D3std6format__T6getNthVAyaa21_736570617261746f72206469676974207769647468SQCu6traits10isIntegralTiTQCxZQDjFNaNfkQDkZi in build.o
      __D3std6format__T6getNthVAyaa19_736570617261746f7220636861726163746572SQCq6traits10isSomeCharTwTQCtZQDfFNaNfkQDgZw in build.o
      __D3std6format__T14formattedWriteTSQBg5stdio4File17LockingTextWriterTaTkZQCeFNfKQBuIAakZk in build.o
      ...
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Error: linker exited with status 1