[flang-driver] Uniquify the target_features string

Use existing clang support for uniquifying target feature lists to pass
a unique list through to flang.

Author: RichBarton-Arm

clang/lib/Driver/ToolChains/ClassicFlang.cpp

@@ -989,11 +989,10 @@ void ClassicFlang::ConstructJob(Compilation &C, const JobAction &JA,
   std::string FeatureList = "";
   getTargetFeatureList(D, Triple, Args, UpperCmdArgs, false, Features);
   if (!Features.empty()) {
-    for (unsigned I = 0, N = Features.size(); I < N; ++I) {
-      StringRef Name = Features[I];
-      FeatureList += Name.str();
-      if (I < (N - 1))
+    for (auto Feature : unifyTargetFeatures(Features)) {
+      if (!FeatureList.empty())
         FeatureList += ',';
+      FeatureList += Feature;
     }
 
     LowerCmdArgs.push_back("-target_features");

clang/test/Driver/emit-flang-attrs.f90

@@ -3,6 +3,7 @@
 // RUN: %flang -### -target aarch64-linux-gnu -march=armv8-a -c %s 2>&1 | FileCheck --check-prefix=CHECK-ATTRS-NEON %s
 // RUN: %flang -### -target aarch64-linux-gnu -march=armv8-a+sve -c %s 2>&1 | FileCheck --check-prefix=CHECK-ATTRS-SVE %s
 // RUN: %flang -### -target aarch64-linux-gnu -march=armv8-a+nosve -c %s 2>&1 | FileCheck --check-prefix=CHECK-ATTRS-NOSVE %s
+// RUN: %flang -### -target aarch64-linux-gnu -march=armv8-a+sve+nosve -c %s 2>&1 | FileCheck --check-prefix=CHECK-ATTRS-NOSVE %s
 // CHECK-ATTRS-NEON: "{{.*}}flang2"
 // CHECK-ATTRS-NEON-SAME: "-target_features" "+neon,+v8a
 // CHECK-ATTRS-SVE: "{{.*}}flang2"