[Issue 4567] dmd should print the dmd.conf location with usage statement

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=4567

--- Comment #8 from hsteoh at quickfur.ath.cx ---
Updated the PR to display the config file along with the usage text, so you can
see it if you run dmd with no input files.

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