[Backtracing] Also update the Linux crash handler, now it's merged.

The Linux crash handler should have the same `output-to` behaviour
as on macOS.

rdar://110371557

Author: al45tair

stdlib/public/runtime/CrashHandlerLinux.cpp

@@ -617,6 +617,8 @@ const char *backtracer_argv[] = {
   "preset",                     // 26
   "--cache",                    // 27
   "true",                       // 28
+  "--output-to",                // 29
+  "stdout",                     // 30
   NULL
 };
 
@@ -769,6 +771,16 @@ run_backtracer(int memserver_fd)
     break;
   }
 
+  switch (_swift_backtraceSettings.outputTo) {
+  case OutputTo::Stdout:
+    backtracer_argv[30] = "stdout";
+    break;
+  case OutputTo::Auto: // Shouldn't happen, but if it does pick stderr
+  case OutputTo::Stderr:
+    backtracer_argv[30] = "stderr";
+    break;
+  }
+
   backtracer_argv[28] = trueOrFalse(_swift_backtraceSettings.cache);
 
   format_unsigned(_swift_backtraceSettings.timeout, timeout_buf);