Fix a wchar.wcstombs_wcrtombs test failure.

Looks like I screwed up a last-minute refactor and didn't re-run the tests.

Change-Id: I90a710ae66a313a9812859650aa0b4e8c6bc57f9
diff --git a/tests/wchar_test.cpp b/tests/wchar_test.cpp
index 0a63b00..d5d27ed 100644
--- a/tests/wchar_test.cpp
+++ b/tests/wchar_test.cpp
@@ -58,8 +58,8 @@
 }
 
 TEST(wchar, wcstombs_wcrtombs) {
-  wchar_t chars[] = { L'h', L'e', L'l', L'l', L'o', 0 };
-  wchar_t bad_chars[] = { L'h', L'i', 666, 0 };
+  const wchar_t chars[] = { L'h', L'e', L'l', L'l', L'o', 0 };
+  const wchar_t bad_chars[] = { L'h', L'i', 666, 0 };
   const wchar_t* src;
   char bytes[BUFSIZ];