[TargetVersion] Only enable on RISC-V and AArch64

clang/include/clang/Basic/Attr.td

@@ -3263,7 +3263,7 @@ def Target : InheritableAttr {
   }];
 }
 
-def TargetVersion : InheritableAttr {
+def TargetVersion : DeclOrTypeAttr, TargetSpecificAttr<TargetArch<!listconcat(TargetAArch64.Arches, TargetRISCV.Arches)>> {
   let Spellings = [GCC<"target_version">];
   let Args = [StringArgument<"NamesStr">];
   let Subjects = SubjectList<[Function], ErrorDiag>;

clang/test/Sema/attr-target-version-unsupported.c

@@ -0,0 +1,4 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown  -fsyntax-only -verify %s
+
+//expected-warning@+1 {{unknown attribute 'target_version' ignored}}
+int __attribute__((target_version("aes"))) foo(void) { return 3; }