swift

4aa516ae - SILGen: Fix `if #available` for unavailable custom domains in zippered modules.

SILGen: Fix `if #available` for unavailable custom domains in zippered modules. When generating SIL for an `if #available(SomeDomain)` query in code being compiled for a zippered target, the generated code was mis-compiled if `SomeDomain` were disabled at compile time. Empty version ranges need to be handled explicitly by `SILGenFunction::emitZipperedOSVersionRangeCheck()`. SILGen still miscompiles `if #unavailable` queries generally in code compiled for a zippered target (rdar://147929876). Resolves rdar://150888941.