[SYCL] Test for PR #7918 - invalid value in named_sub_group_size

When PR #7918 was submitted, a test wasn't added along with it.

Author: premanandrao

clang/test/SemaSYCL/sub-group-size2.cpp

@@ -0,0 +1,12 @@
++// RUN: %clang_cc1 -fsycl-is-device -sycl-std=2020 -fsyntax-only %s -ast-dump -Wno-ignored-attributes | FileCheck %s
++
++// Check that when an invalid value is specified for the attribute
++// intel::named_sub_group_size, an invalid value is not added to the
++// function declaration.
++
++// CHECK: FunctionDecl {{.*}} f1 'void ()'
++// CHECK-NOT: IntelNamedSubGroupSizeAttr
++[[intel::named_sub_group_size(invalid)]] void f1();
++// CHECK: FunctionDecl {{.*}} f2 'void ()'
++// CHECK-NOT: IntelNamedSubGroupSizeAttr
++[[intel::named_sub_group_size("invalid string")]] void f2();