test: explicitly size enumeration

On certain targets, enumerations may be smaller than an `unsigned long`.
Use an explicitly sized enumeration.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@295558 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/libcxx/type_traits/convert_to_integral.pass.cpp b/test/libcxx/type_traits/convert_to_integral.pass.cpp
index 3fdc98f..8cac0c7 100644
--- a/test/libcxx/type_traits/convert_to_integral.pass.cpp
+++ b/test/libcxx/type_traits/convert_to_integral.pass.cpp
@@ -76,7 +76,7 @@
 
 
 enum enum1 { zero = 0, one = 1 };
-enum enum2 {
+enum enum2 : unsigned long {
   value = std::numeric_limits<unsigned long>::max()
 };