Update options to include the new SwiftSynthesizeInterfaceOption flag.

This is the companion of swiftlang/swift#76872.

I've reused the `SwiftIndentOption` constant, which was removed by
swiftlang/swift#76577 (but Options.swift
was never updated here to remove it).

Author: allevato

Sources/SwiftOptions/Option.swift

@@ -25,7 +25,7 @@ public struct OptionAttributes: OptionSet, Hashable {
   public static let doesNotAffectIncrementalBuild = OptionAttributes(rawValue: 0x20)
   public static let autolinkExtract               = OptionAttributes(rawValue: 0x40)
   public static let moduleWrap                    = OptionAttributes(rawValue: 0x80)
-  public static let indent                        = OptionAttributes(rawValue: 0x100)
+  public static let synthesizeInterface           = OptionAttributes(rawValue: 0x100)
   public static let argumentIsPath                = OptionAttributes(rawValue: 0x200)
   public static let moduleInterface               = OptionAttributes(rawValue: 0x400)
   public static let supplementaryOutput           = OptionAttributes(rawValue: 0x800)