Export - arches option should match new behavior of --configurations

[rewrking]

-a was added to export, but it doesn't work correctly. It should work the same way that -c does right now.

The behavior should be as follows:

chalet export -a arm64 clion        # export only 'arm64'
chalet export -a arm64,x86_64 clion # export 'arm64' and 'x86_64'
chalet export clion                 # export all architectures  - 'arm64', 'x86_64', and 'universal' on mac / apple-llvm

Check Xcode project generation - might have to ignore this there.

[rewrking]

Note: Code::Blocks doesn't support this.