[next] Add cmake option to tell whether architectures should be included by default

[JornVernee]

next branch port of #1463

[aquynh]

merged, thanks!

[aquynh]

i had to fix this:

• chmod +x
• add #!/bin/sh
• add missing ;; after RISCV line
• correct the check on input architecture

see 8216e8f

[JornVernee]

@aquynh Ok, sorry about that. I used git bash to test the other PR, but kind of eye-balled this one (should have tested as well).

[aquynh]

The others had similar problem, i fixed them too :-)