official activate script is super confusing

[Chris Katko]

https://dlang.org/install.html#activate

I ran the two curl liners for grabbing DMD and LDC newest.

So now I have ~/dlang/ldc-1.32.2 and ~/dlang/dmd-2.104.0

How am I supposed to have both "activated"? Why does LDC have to 
override DMD, and DMD have to override LDC in the PATH?

I have both installed on another system without using this script 
and they run fine side-by-side. I can call dmd, or ldc, without 
any special "activate" calls. But this script seems to be the 
easiest/fastest way to download DMD and LDC.

I normally have separate scripts for dmd and ldc. (godmd, and 
goldc) But it seems I'll have to hardcode calls to the right 
activate script before my normal script code.

```sh
#godmd
~/dlang/dmd-2.104.0/activate
dmd -I.......
```

But the activate scripts may have different version numbers in 
path!

~/dlang/dmd-2.104.0/activate

will one day become

~/dlang/dmd-2.105.0/activate

and so on.