[embedded] Fix editor placeholders by adding a StaticString variant of _undefined

Author: kubamracek

stdlib/public/core/AssertCommon.swift

@@ -252,6 +252,7 @@ func _unimplementedInitializer(className: StaticString,
   Builtin.int_trap()
 }
 
+/// Used to evaluate editor placeholders.
 @_unavailableInEmbedded
 public // COMPILER_INTRINSIC
 func _undefined<T>(
@@ -261,6 +262,15 @@ func _undefined<T>(
   _assertionFailure("Fatal error", message(), file: file, line: line, flags: 0)
 }
 
+/// Used to evaluate editor placeholders.
+public // COMPILER_INTRINSIC
+func _undefined<T>(
+  _ message: @autoclosure () -> StaticString = StaticString(),
+  file: StaticString = #file, line: UInt = #line
+) -> T {
+  _assertionFailure("Fatal error", message(), file: file, line: line, flags: 0)
+}
+
 /// Called when falling off the end of a switch and the type can be represented
 /// as a raw value.
 ///