[libc] Revert rounding mode changes for hermetic tests

[jhuber6]

Summary

We got rid of the rounding mode here so that the hermetic tests wouldn't
depend on the system fenv.h. But this seemed to cause some bots to
break. Getting rid of this change for now, it should be fine for the CPU
builds.

libc/test/UnitTest/RoundingModeUtils.cpp

 //===-- RoundingModeUtils.cpp ---------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "RoundingModeUtils.h"
 
-#include "src/__support/FPUtil/FEnvImpl.h"
+#include <fenv.h>
 
 namespace __llvm_libc {
 namespace fputil {
 namespace testing {
 
 int get_fe_rounding(RoundingMode mode) {
   switch (mode) {
   case RoundingMode::Upward:
case RoundingMode::Nearest:
     return FE_TONEAREST;
     break;
   default:
     __builtin_unreachable();
   }
 }
 
 ForceRoundingMode::ForceRoundingMode(RoundingMode mode) {
-  old_rounding_mode = fputil::get_round();
+  old_rounding_mode = fegetround();
   rounding_mode = get_fe_rounding(mode);
   if (old_rounding_mode != rounding_mode)
-    fputil::set_round(rounding_mode);
+    fesetround(rounding_mode);
 }
 
 ForceRoundingMode::~ForceRoundingMode() {
   if (old_rounding_mode != rounding_mode)
-    fputil::set_round(old_rounding_mode);
+    fesetround(old_rounding_mode);
 }
 
 } // namespace testing
 } // namespace fputil
 } // namespace __llvm_libc