[flang] Move .f77 to the list of fixed-form file extension

[awarzynski]

Summary

The free form was introduced in Fortran 90, so treating .f77 as free-form was a bug.

[arnamoy10]

LGTM

[kiranktp]

LGTM

[kiranchandramohan]

LGTM.

flang/lib/Frontend/FrontendOptions.cpp

 //===- FrontendOptions.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 "flang/Frontend/FrontendOptions.h"
 #include "flang/Evaluate/expression.h"
 
 using namespace Fortran::frontend;
 
 bool Fortran::frontend::isFixedFormSuffix(llvm::StringRef suffix) {
   // Note: Keep this list in-sync with flang/test/lit.cfg.py
-  return suffix == "f" || suffix == "F" || suffix == "ff" || suffix == "for" ||
-      suffix == "FOR" || suffix == "fpp" || suffix == "FPP";
+  return suffix == "f77" || suffix == "f" || suffix == "F" || suffix == "ff" ||
+      suffix == "for" || suffix == "FOR" || suffix == "fpp" || suffix == "FPP";
 }
 
 bool Fortran::frontend::isFreeFormSuffix(llvm::StringRef suffix) {
   // Note: Keep this list in-sync with flang/test/lit.cfg.py
   // TODO: Add Cuda Fortan files (i.e. `*.cuf` and `*.CUF`).
-  return suffix == "f77" || suffix == "f90" || suffix == "F90" ||
-      suffix == "ff90" || suffix == "f95" || suffix == "F95" ||
-      suffix == "ff95" || suffix == "f03" || suffix == "F03" ||
-      suffix == "f08" || suffix == "F08" || suffix == "f18" || suffix == "F18";
+  return suffix == "f90" || suffix == "F90" || suffix == "ff90" ||
+      suffix == "f95" || suffix == "F95" || suffix == "ff95" ||
+      suffix == "f03" || suffix == "F03" || suffix == "f08" ||
+      suffix == "F08" || suffix == "f18" || suffix == "F18";
 }
 
 // TODO: This is a copy of `asFortran` from f18.cpp and is added here for
 // compatiblity. It doesn't really belong here, but I couldn't find a better
 // place. We should decide whether to add it to the Evaluate or Parse/Unparse
 // APIs or some dedicated utility library in the driver.
 Fortran::parser::AnalyzedObjectsAsFortran
 Fortran::frontend::getBasicAsFortran() {