Trivial indentation fix.
LDMD: Create output directories if they do not exist.

There might be other cases using the LLVM output code as well
that I haven't handled here, but the changes are sufficient to
make LDC work with rdmd on Linux.

GitHub: Fixes #480.
Merge pull request #482 from klickverbot/ldmd-create-directory

LDMD: Create output directories if they do not exist.