Replace #if swift(>=6.0) guards with #if compiler(>=6.0).

All uses of `internal import` were previously garuded with `#if swift(>=6.0)`,
presumably to handle differences in compiler support for `internal import`.
However, `#if swift(>=)` is not the correct directive to use for this purpose,
as it primarily tests the language mode that is enabled. These existing
conditionals never evaluated true when building this package since it is not
configured to build with Swift 6 enabled. Instead, use `#if compiler(>=6.0)`
which correctly predicates the imports on only the compiler version.

Author: tshortli

Sources/ArgumentParser/Completions/BashCompletionsGenerator.swift

@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import ArgumentParserToolInfo
 #else
 import ArgumentParserToolInfo

Sources/ArgumentParser/Completions/CompletionsGenerator.swift

@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import ArgumentParserToolInfo
 internal import Foundation
 #else

Sources/ArgumentParser/Completions/FishCompletionsGenerator.swift

@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import ArgumentParserToolInfo
 internal import Foundation
 #else

Sources/ArgumentParser/Completions/ZshCompletionsGenerator.swift

@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import ArgumentParserToolInfo
 internal import Foundation
 #else

Sources/ArgumentParser/Parsable Types/ParsableArguments.swift

@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import Foundation
 #else
 import Foundation

Sources/ArgumentParser/Parsing/CommandParser.swift

@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 #if canImport(Dispatch)
 @preconcurrency private import class Dispatch.DispatchSemaphore
 #endif

Sources/ArgumentParser/Usage/DumpHelpGenerator.swift

@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import ArgumentParserToolInfo
 internal import class Foundation.JSONEncoder
 #else

Sources/ArgumentParser/Usage/MessageInfo.swift

@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import protocol Foundation.LocalizedError
 internal import class Foundation.NSError
 #else

Sources/ArgumentParser/Usage/UsageGenerator.swift

@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import protocol Foundation.LocalizedError
 #else
 import protocol Foundation.LocalizedError

Sources/ArgumentParser/Utilities/Mutex.swift

@@ -9,7 +9,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=6.0)
+#if compiler(>=6.0)
 internal import Foundation
 #else
 import Foundation