[libcxx] Get categories.collate tests passing on linux.

[EricWF]

Summary

GLIBC collates en_US differently than Apple libc. Perhaps we should just XFAIL.

[mclow.lists]

This looks fine to me, with the proviso (again), that we should try to figure out what's the *correct* behavior, if there is one.

test/localization/locale.categories/category.collate/locale.collate.byname/compare.pass.cpp

 
 int main()
 {
+    // Ensure that the default locale is known. Othewise the second test could fail.
+    putenv(const_cast<char*>("LANG=" LOCALE_en_US_UTF_8));
+    // GLIBC collates en_US differently
+#if !defined(__GLIBC__)
+    int const expect = 1;
+#else
+    int const expect = -1;
+#endif
     {
         std::locale l(LOCALE_en_US_UTF_8);
         {

             std::string s2("aaaaaaA");
             std::string s3("BaaaaaA");
             assert(f.compare(s2.data(), s2.data() + s2.size(),
-                             s3.data(), s3.data() + s3.size()) == 1);
+                             s3.data(), s3.data() + s3.size()) == expect);
         }
         {
             const std::collate<wchar_t>& f = std::use_facet<std::collate<wchar_t> >(l);
             std::wstring s2(L"aaaaaaA");
             std::wstring s3(L"BaaaaaA");
             assert(f.compare(s2.data(), s2.data() + s2.size(),
-                             s3.data(), s3.data() + s3.size()) == 1);
+                             s3.data(), s3.data() + s3.size()) == expect);
         }
     }
     {

             std::string s2("aaaaaaA");
             std::string s3("BaaaaaA");
             assert(f.compare(s2.data(), s2.data() + s2.size(),
-                             s3.data(), s3.data() + s3.size()) == 1);
+                             s3.data(), s3.data() + s3.size()) == expect);
         }
         {
             const std::collate<wchar_t>& f = std::use_facet<std::collate<wchar_t> >(l);
             std::wstring s2(L"aaaaaaA");
             std::wstring s3(L"BaaaaaA");
             assert(f.compare(s2.data(), s2.data() + s2.size(),
-                             s3.data(), s3.data() + s3.size()) == 1);
+                             s3.data(), s3.data() + s3.size()) == expect);
         }
     }
     {