[gcc r11-1730] testsuite: fix constexpr-is_literal.C deprecated c++17 and above.

[David Edelsohn]

https://gcc.gnu.org/g:7d503e329911a9c7f6d4db3170f6ed6f5a0424ba

commit r11-1730-g7d503e329911a9c7f6d4db3170f6ed6f5a0424ba
Author: David Edelsohn <dje.gcc@gmail.com>
Date:   Mon Jun 29 20:41:55 2020 -0400

    testsuite: fix constexpr-is_literal.C deprecated c++17 and above.
    
    std::is_literal_type is deprecated in C++17 and above.
    
    This was introduced in c++11, but the testsuite list of standards now only
    includes c++98 and c++14.  This patch limits the test to c++14_only to
    prevent deprecation warnings.
    
    gcc/testsuite/ChangeLog
    
    2020-06-30  David Edelsohn  <dje.gcc@gmail.com>
    
            * g++.dg/cpp0x/constexpr-is_literal.C: Limit test to -std=c++14.

Diff:
---
 gcc/testsuite/g++.dg/cpp0x/constexpr-is_literal.C | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-is_literal.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-is_literal.C
index f255b8d1507..02d2ca35298 100644
--- a/gcc/testsuite/g++.dg/cpp0x/constexpr-is_literal.C
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-is_literal.C
@@ -1,4 +1,4 @@
-// { dg-do compile { target c++11 } }
+// { dg-do compile { target c++14_only } }
 
 #include <type_traits>