is_convertible_without_narrowing static assert is failing in some cases with GCC v7.3.1

[lydia-at-amazon]

When building with GCC v7.3.1, a number of static asserts in type_traits_ext.hpp and test_type_traits_ext.cpp fail:

include/cetl/type_traits_ext.hpp:125:1: error: static assertion failed: self-test failure
static_assert(is_convertible_without_narrowing<int, long long>::value, "self-test failure");
^~~~~~~~~~~~~

cetlvast/suites/unittest/test_type_traits_ext.cpp:53:1: error: static assertion failed
static_assert(is_convertible_without_narrowing<int, long long>::value, "");
^~~~~~~~~~~~~

cetlvast/suites/unittest/test_type_traits_ext.cpp:56:1: error: static assertion failed
static_assert(is_convertible_without_narrowing<float, long double>::value, "");
^~~~~~~~~~~~~

cetlvast/suites/unittest/test_type_traits_ext.cpp:71:1: error: static assertion failed
static_assert(!is_convertible_without_narrowing<long, foo_val>::value, "");
^~~~~~~~~~~~~

cetlvast/suites/unittest/test_type_traits_ext.cpp:73:1: error: static assertion failed
static_assert(!is_convertible_without_narrowing<long, foo_ref>::value, "");
^~~~~~~~~~~~~

cetlvast/suites/unittest/test_type_traits_ext.cpp:99:1: error: static assertion failed
static_assert(
^~~~~~~~~~~~~