remove shorthand of --skip-initial-build

[lxe]

-s is already taken by --source-maps

I missed that unfortunately in my previous PR: #3489

[lxe]

Fortunately this just breaks the shorthand of --skip-initial-build and doesn't affect the correct behavior of -s and --source-maps

[loganfsmyth]

Ahh good catch. Part of me wonders if it might be clearer to skip the shorthand for this entirely since -S overloading -s with two options that are very unrelated seems likely to confuse users.

[loganfsmyth]

Thanks!