Merge pull request swiftlang#75959 from hyp/eng/cxx-string-fix

[cxx][windows] fix the CxxStdlib build for recent MSVC versions after…

Author: compnerd

stdlib/public/Cxx/std/String.swift

@@ -21,13 +21,27 @@ extension std.string {
   ///   Swift string.
   public init(_ string: String) {
     self = string.withCString(encodedAs: UTF8.self) { buffer in
+#if os(Windows)
+      // Use the 2 parameter constructor.
+      // The MSVC standard library has a enable_if template guard
+      // on the 3 parameter constructor, and thus it's not imported into Swift.
+      std.string(buffer, string.utf8.count)
+#else
       std.string(buffer, string.utf8.count, .init())
+#endif
     }
   }
 
   public init(_ string: UnsafePointer<CChar>?) {
     if let str = string {
+#if os(Windows)
+      // Use the 2 parameter constructor.
+      // The MSVC standard library has a enable_if template guard
+      // on the 3 parameter constructor, and thus it's not imported into Swift.
+      self.init(str, UTF8._nullCodeUnitOffset(in: str))
+#else
       self.init(str, UTF8._nullCodeUnitOffset(in: str), .init())
+#endif
     } else {
       self.init()
     }