[OpenMP] Properly handle the -f/-fno veraints for the new driver

Summary:
We provide the `-f(no-)openmp-new-driver` option to allow users to use
the old or new driver. Previously this wasn't handled in the expected
way and only `-fno-openmp-new-driver` was checked. This patch fixes that
by using the `hasFlag` method as is standard.

Author: jhuber6

clang/lib/Driver/Driver.cpp

@@ -3984,7 +3984,8 @@ void Driver::BuildActions(Compilation &C, DerivedArgList &Args,
 
   bool UseNewOffloadingDriver =
       C.isOffloadingHostKind(Action::OFK_OpenMP) &&
-      !Args.hasArg(options::OPT_fno_openmp_new_driver);
+      Args.hasFlag(options::OPT_fopenmp_new_driver,
+                   options::OPT_fno_openmp_new_driver, true);
 
   for (auto &I : Inputs) {
     types::ID InputType = I.first;

clang/lib/Driver/ToolChains/Clang.cpp

@@ -4675,7 +4675,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     if (IsUsingLTO) {
       // Only AMDGPU supports device-side LTO.
       if (IsDeviceOffloadAction &&
-          Args.hasArg(options::OPT_fno_openmp_new_driver) &&
+          !Args.hasFlag(options::OPT_fopenmp_new_driver,
+                        options::OPT_fno_openmp_new_driver, true) &&
           !Triple.isAMDGPU()) {
         D.Diag(diag::err_drv_unsupported_opt_for_target)
             << Args.getLastArg(options::OPT_foffload_lto,