move to checker error, rather than panic

src/check_builtin.cpp

@@ -4714,6 +4714,14 @@ gb_internal bool check_builtin_procedure(CheckerContext *c, Operand *operand, As
 		break;
 
 	case BuiltinProc_read_cycle_counter_frequency:
+		if (build_context.metrics.arch != TargetArch_arm64) {
+			error(call, "'%.*s' is only allowed on arm64 targets", LIT(builtin_name));
+			return false;
+		}
+		operand->mode = Addressing_Value;
+		operand->type = t_i64;
+		break;
+
 	case BuiltinProc_read_cycle_counter:
 		operand->mode = Addressing_Value;
 		operand->type = t_i64;

src/llvm_backend_proc.cpp

@@ -2820,8 +2820,6 @@ gb_internal lbValue lb_build_builtin_proc(lbProcedure *p, Ast *expr, TypeAndValu
 				LLVMValueRef the_asm = llvm_get_inline_asm(func_type, str_lit("mrs $0, cntfrq_el0"), str_lit("=r"), has_side_effects);
 				GB_ASSERT(the_asm != nullptr);
 				res.value = LLVMBuildCall2(p->builder, func_type, the_asm, nullptr, 0, "");
-			} else {
-				GB_PANIC("Unsupported architecture: %.*s", LIT(target_arch_names[build_context.metrics.arch]));
 			}
 
 			return res;