The DMD compiler is under development, so it is a moving target.
To determine what commandline your version of CodeBlocks uses, enable full logging:
Settings -> Compiler and debugger
Selected compiler = Digital Mars D Compiler
Tab "Other"
Compiler logging = Full command line
My version of CB (svn 3295) uses "-ofobj\Debug\hello.obj" for the hello-world example produced by the wizard, which makes me think that you should probably just download a fresh nightly of CB.
I'm using DMD version 0.173
Regards,