Wrong 64b compiler flag passed to LDC2

[p0nce]

When using --compiler=ldc2 with --arch=x86_64, DUB passes x86_64 to ldc2 instead of x86-64 which it expects.
Workaround: using --compiler=ldmd2.

[MartinNowak]

Code is here https://github.com/D-Programming-Language/dub/blob/0dc606ec9383b1c578b9896bfdf4c946cf485c92/source/dub/compilers/ldc.d#L71.