[libcxx][test] Only call valarray::min and ::max on empty containers when testing libc++

[CaseyCarter]

Summary

valarray:min and valarray::max have preconditions that require the valarray to be non-empty, so these calls are inherently non-portable.

[ldionne]

You can go ahead and commit this.

test/std/numerics/numarray/template.valarray/valarray.members/min.pass.cpp

29

typo: size() > 0

[CaseyCarter]

@STL_MSFT seems to have already fixed this by removing the problem test cases in bf7dc572f199007cbe042d5ea41bcf873dcedd8f. I'll simply abandon this change.

test/std/numerics/numarray/template.valarray/valarray.members/max.pass.cpp

 {
     {
         typedef double T;
         T a1[] = {1.5, 2.5, -3, 4, -5.5};
         const unsigned N1 = sizeof(a1)/sizeof(a1[0]);
         std::valarray<T> v1(a1, N1);
         assert(v1.max() == 4.0);
     }
+#ifdef _LIBCPP_VERSION // Not portable: valarray::max requires size() > 0
     {
         typedef double T;
         std::valarray<T> v1;
         v1.max();
     }
+#endif // _LIBCPP_VERSION
     {
         typedef double T;
         T a1[] = {1.5, 2.5, -3, 4, -5.5};
         const unsigned N1 = sizeof(a1)/sizeof(a1[0]);
         std::valarray<T> v1(a1, N1);
         assert((2*v1).max() == 8.0);
     }
 
     return 0;
 }

test/std/numerics/numarray/template.valarray/valarray.members/min.pass.cpp

 {
     {
         typedef double T;
         T a1[] = {1.5, 2.5, -3, 4, 5.5};
         const unsigned N1 = sizeof(a1)/sizeof(a1[0]);
         std::valarray<T> v1(a1, N1);
         assert(v1.min() == -3.0);
     }
+#ifdef _LIBCPP_VERSION // Not portable: valarray::min requires size() >
     {
         typedef double T;
         std::valarray<T> v1;
         v1.min();
     }
+#endif // _LIBCPP_VERSION
     {
         typedef double T;
         T a1[] = {1.5, 2.5, -3, 4, 5.5};
         const unsigned N1 = sizeof(a1)/sizeof(a1[0]);
         std::valarray<T> v1(a1, N1);
         assert((2*v1).min() == -6.0);
     }
 
     return 0;
 }