how to conditionally compile swift according to the branch

Question

I konw there is a way like this:

#if DEBUG
let a = 2
#else
let a = 3
#endif

but I want ask,

I there a way to fully control the symbol by build step script?

So that I cant test my git branch and decide which symbol to use:

something like:

#if DEVELOP
let server = "dev.domain.com"
#elseif MASTER
let server = "test.domain.com"
#elseif PRODUCTION
let server = "prod.domain.com"
#elseif NEW_FEATURE
let server = "feature.domain.com"
#endif