Global version/debug statements in file?

[cc via Digitalmars-d-learn]

Is there some way to globally declare version= or debug= 
statements in a file and have them apply to the entire project 
being compiled?  As the documentation says these only apply to 
the module scope they exist in, and need to be added to the 
command line otherwise.  It would be a bit easier for me to 
maintain a separate .d source file when I want to add/comment out 
statements for testing than to keep updating the build command 
line.  I tried using a mixin, such as:

// constants.d
module constants;
enum VERSIONS = q{
        version=Compress;
};
// main.d
import constants;
mixin(VERSIONS);
void main() {
        version(Compress)
                writeln("Compress it!");
        version(Decompress)
                writeln("Decompress it!");
}

This does seem to work inside function bodies, but not at module 
scope in the importing file.  e.g.:

// main.d
import constants;
mixin(VERSIONS)
version(Compress) {
        ...
}

Gives: Error: version `Compress` defined after use