Commands: enable the parseable module interface by default

Enable the swift module interface to be emitted by default.  This is
helpful for API surface tracking and can potentially enable perusal of
the swiftinterface in VSCode mirroring what XCode already permits.

Author: compnerd

Sources/Commands/Options.swift

@@ -319,8 +319,8 @@ struct BuildOptions: ParsableArguments {
     var indexStoreMode: StoreMode = .autoIndexStore
 
     /// Whether to enable generation of `.swiftinterface`s alongside `.swiftmodule`s.
-    @Flag(name: .customLong("enable-parseable-module-interfaces"))
-    var shouldEnableParseableModuleInterfaces: Bool = false
+    @Flag(name: .customLong("parseable-module-interfaces"), inversion: .prefixedEnableDisable)
+    var shouldEnableParseableModuleInterfaces: Bool = true
 
     /// The number of jobs for llbuild to start (aka the number of schedulerLanes)
     @Option(name: .shortAndLong, help: "The number of jobs to spawn in parallel during the build process")