[flang][driver] Remove unnecessary includes in the unittest

[DavidTruby]

LGTM, perhaps put NFC in the commit message?

[awarzynski]

In D88219#2292353, @DavidTruby wrote:

LGTM, perhaps put NFC in the commit message?

Ta, commit msg updated!

[CarolineConcatto]

flang/unittests/Frontend/CompilerInstanceTest.cpp

23

Don't we need to include #include "llvm/Support/raw_ostream.h"?

[DavidTruby]

flang/unittests/Frontend/CompilerInstanceTest.cpp

23

This builds for me so I assume it's transitively included by one of the other includes. Probably "flang/Frontend/CompilerInstance.h"?

[awarzynski]

flang/unittests/Frontend/CompilerInstanceTest.cpp

23

My bad - I searched the file for raw_ostream, but I should've searched for raw_string_ostream instead, sorry! raw_ostream.h is included via TextDiagnosticPrinter.h, so the test will continue to work.

flang/unittests/Frontend/CompilerInstanceTest.cpp

 //===- unittests/Frontend/CompilerInstanceTest.cpp - CI tests -------------===//
 //
 // 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 "flang/Frontend/CompilerInstance.h"
-#include "gtest/gtest.h"
-#include "flang/Frontend/CompilerInvocation.h"
 #include "clang/Basic/DiagnosticOptions.h"
-#include "clang/Driver/Options.h"
 #include "clang/Frontend/TextDiagnosticPrinter.h"
-#include "llvm/Support/raw_ostream.h"
 
-#include <filesystem>
+#include "gtest/gtest.h"
+
 using namespace llvm;
 using namespace Fortran::frontend;
 
 namespace {
 
 TEST(CompilerInstance, AllowDiagnosticLogWithUnownedDiagnosticConsumer) {
   // 1. Set-up a basic DiagnosticConsumer
   std::string diagnosticOutput;
   llvm::raw_string_ostream diagnosticsOS(diagnosticOutput);
   auto diagPrinter = std::make_unique<clang::TextDiagnosticPrinter>(
       diagnosticsOS, new clang::DiagnosticOptions());
 
   // 2. Create a CompilerInstance (to manage a DiagnosticEngine)
   CompilerInstance compInst;
 
   // 3. Set-up DiagnosticOptions
   auto diagOpts = new clang::DiagnosticOptions();