Linking external functions?

[DLearner]

Wanted to try out linking two source files independantly compiled.

ExtCallee.d source file:
```
extern(C) void ExtCallee() {
    import std.stdio;

    writeln("Entered: ", __FUNCTION__);
    writeln("Exiting: ", __FUNCTION__);
}
```
ExtMain.d source file:
```
void main() {
    import std.stdio;
    extern(C) void ExtCallee();


    writeln("Entered: ", __FUNCTION__);

    ExtCallee();

    writeln("Exiting: ", __FUNCTION__);
}
```
Then:
```
dmd ExtCallee -c
```
which worked, producing .obj file.

However:
```
dmd ExtCallee.obj -run ExtMain
lld-link: error: undefined symbol: __D7ExtMain4mainFZ9ExtCalleeUZv
>>> referenced by ExtMain.obj:(__Dmain)
Error: linker exited with status 1
```

Ideas?