StdlibUnittest: add a workraound for DOS lineendings

Windows uses DOS line endings which appear through the PIPE endpoints.
We currently split on line feeds only, leaving the carriage return in
place.  Without this, the messages on the communication pipe would not
be interpreted correctly.

Author: compnerd

stdlib/private/StdlibUnittest/StdlibUnittest.swift

@@ -1029,6 +1029,8 @@ class _ParentProcess {
                               omittingEmptySubsequences: false)
         switch controlMessage[1] {
         case "expectCrash":
+          fallthrough
+        case "expectCrash\r":
           if isStdout {
             stdoutSeenCrashDelimiter = true
             anyExpectFailedInChild = controlMessage[2] == "true"
@@ -1037,6 +1039,8 @@ class _ParentProcess {
             expectingPreCrashMessage = String(controlMessage[2])
           }
         case "end":
+          fallthrough
+        case "end\r":
           if isStdout {
             stdoutEnd = true
             anyExpectFailedInChild = controlMessage[2] == "true"