[libcxx] [test] Use the native path types in path.compare

This makes sure that it actually tests the right compare() overloads
in windows configurations.

This also fixes the allocation guards that enforce no allocations
while running the compare() functions.

Differential Revision: https://reviews.llvm.org/D97551

Author: mstorsjo

libcxx/test/std/input.output/filesystems/class.path/path.member/path.compare.pass.cpp

@@ -85,16 +85,18 @@ void test_compare_basic()
   for (auto const & TC : CompareTestCases) {
     const path p1(TC.LHS);
     const path p2(TC.RHS);
-    const std::string R(TC.RHS);
-    const std::string_view RV(TC.RHS);
+    std::string RHS(TC.RHS);
+    const path::string_type R(RHS.begin(), RHS.end());
+    const std::basic_string_view<path::value_type> RV(R);
+    const path::value_type *Ptr = R.c_str();
     const int E = TC.expect;
     { // compare(...) functions
       DisableAllocationGuard g; // none of these operations should allocate
 
       // check runtime results
       int ret1 = normalize_ret(p1.compare(p2));
       int ret2 = normalize_ret(p1.compare(R));
-      int ret3 = normalize_ret(p1.compare(TC.RHS));
+      int ret3 = normalize_ret(p1.compare(Ptr));
       int ret4 = normalize_ret(p1.compare(RV));
 
       g.release();