[flang] Improve output from a STOP statement

[klausler]

Summary

Add a missing newline to IEEE FP flag formatting, and
don't neglect to emit STOP when there's no code number.

flang/runtime/stop.cpp

if (excepts & FE_INVALID) {
       std::fputs(" INVALID", stderr);
     }
     if (excepts & FE_OVERFLOW) {
       std::fputs(" OVERFLOW", stderr);
     }
     if (excepts & FE_UNDERFLOW) {
       std::fputs(" UNDERFLOW", stderr);
     }
+    std::fputc('\n', stderr);
   }
 }
 
 static void CloseAllExternalUnits(const char *why) {
   Fortran::runtime::io::IoErrorHandler handler{why};
   Fortran::runtime::io::ExternalFileUnit::CloseAll(handler);
 }
 
 [[noreturn]] void RTNAME(StopStatement)(
     int code, bool isErrorStop, bool quiet) {
   CloseAllExternalUnits("STOP statement");
   if (!quiet) {
+    std::fprintf(stderr, "Fortran %s", isErrorStop ? "ERROR STOP" : "STOP");
     if (code != EXIT_SUCCESS) {
-      std::fprintf(stderr, "Fortran %s: code %d\n",
-          isErrorStop ? "ERROR STOP" : "STOP", code);
+      std::fprintf(stderr, ": code %d\n", code);
     }
+    std::fputc('\n', stderr);
     DescribeIEEESignaledExceptions();
   }
   std::exit(code);
 }
 
 [[noreturn]] void RTNAME(StopStatementText)(
     const char *code, bool isErrorStop, bool quiet) {
   CloseAllExternalUnits("STOP statement");