[Issue 21786] New: install.sh: Add error for trying to install two compilers

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21786

          Issue ID: 21786
           Summary: install.sh: Add error for trying to install two
                    compilers
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: installer
          Assignee: nobody at puremagic.com
          Reporter: john.michael.hall at gmail.com

A command like

~/dlang/install.sh install ldc,dub

installs ldc and a corresponding version of dub. However, install.sh does not
support commands here other than dub. For instance, a call like

~/dlang/install.sh install ldc,dmd

will return errors like

Downloading and unpacking
https://github.com/dlang/dub/releases/download/v/dub-v-linux-x86_64.tar.gz
curl: (22) The requested URL returned error: 404  

Instead, there should be a check that anything after the comma starts with dub
and have an error if it is not. 

Alternately, it could loop through anything comma'ed so that the above command
installs both ldc and dmd.

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