[libc++][hardening] Clean up some legacy debug mode tests: (#71016)

- reenable a few tests that still pass under the new debug mode;
- delete a placeholder test;
- delete a test that is no longer relevant.

Author: var-const

libcxx/test/libcxx/algorithms/debug_less.inconsistent.pass.cpp

@@ -12,8 +12,8 @@
 
 // Make sure __debug_less asserts when the comparator is not consistent.
 
-// REQUIRES: has-unix-headers
-// UNSUPPORTED: !libcpp-has-legacy-debug-mode, c++03
+// REQUIRES: has-unix-headers, libcpp-hardening-mode=debug
+// UNSUPPORTED: c++03
 
 #include <algorithm>
 #include <iterator>

libcxx/test/libcxx/algorithms/debug_less.pass.cpp

@@ -12,8 +12,8 @@
 
 // __debug_less checks that a comparator actually provides a strict-weak ordering.
 
-// REQUIRES: has-unix-headers
-// UNSUPPORTED: !libcpp-has-legacy-debug-mode, c++03
+// REQUIRES: has-unix-headers, libcpp-hardening-mode=debug
+// UNSUPPORTED: c++03
 
 #include <algorithm>
 #include <cassert>

libcxx/test/libcxx/algorithms/debug_three_way_comp.inconsistent.pass.cpp

@@ -12,7 +12,8 @@
 
 // Make sure __debug_three_way_comp asserts when the comparator is not consistent.
 
-// UNSUPPORTED: !libcpp-has-legacy-debug-mode, c++03, c++11, c++14, c++17
+// REQUIRES: libcpp-hardening-mode=debug
+// UNSUPPORTED: c++03, c++11, c++14, c++17
 
 #include <algorithm>
 #include <iterator>

libcxx/test/libcxx/debug/containers/associative_containers.pass.cpp

@@ -6,8 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: !libcpp-has-legacy-debug-mode, c++03, c++11, c++14
-// REQUIRES: has-unix-headers
+// UNSUPPORTED: c++03, c++11, c++14
+// REQUIRES: has-unix-headers, libcpp-hardening-mode=debug
 
 // <memory_resource>
 

libcxx/test/libcxx/debug/extern-templates.sh.cpp

@@ -708,7 +708,6 @@ libcxx/test/libcxx/containers/views/views.span/span.elem/assert.op_idx.pass.cpp
 libcxx/test/libcxx/containers/views/views.span/span.sub/assert.first.pass.cpp
 libcxx/test/libcxx/containers/views/views.span/span.sub/assert.last.pass.cpp
 libcxx/test/libcxx/containers/views/views.span/span.sub/assert.subspan.pass.cpp
-libcxx/test/libcxx/debug/containers/associative_containers.pass.cpp
 libcxx/test/libcxx/debug/containers.multithread.pass.cpp
 libcxx/test/libcxx/debug/containers/sequence_container_iterators.pass.cpp
 libcxx/test/libcxx/debug/containers/string.pass.cpp

libcxx/test/libcxx/utilities/utility/mem.res/mem.poly.allocator.class/mem.poly.allocator.mem/debug.deallocate.pass.cpp

@@ -136,24 +136,6 @@ def _getAndroidDeviceApi(cfg):
           """,
         ),
     ),
-    # Some tests rely on creating shared libraries which link in the C++ Standard Library. In some
-    # cases, this doesn't work (e.g. if the library was built as a static archive and wasn't compiled
-    # as position independent). This feature informs the test suite of whether it's possible to create
-    # a shared library in a shell test by using the '-shared' compiler flag.
-    #
-    # Note: To implement this check properly, we need to make sure that we use something inside the
-    # compiled library, not only in the headers. It should be safe to assume that all implementations
-    # define `operator new` in the compiled library.
-    Feature(
-        name="cant-build-shared-library",
-        when=lambda cfg: not sourceBuilds(
-            cfg,
-            """
-            void f() { new int(3); }
-          """,
-            ["-shared"],
-        ),
-    ),
     # Check for a Windows UCRT bug (fixed in UCRT/Windows 10.0.20348.0):
     # https://developercommunity.visualstudio.com/t/utf-8-locales-break-ctype-functions-for-wchar-type/1653678
     Feature(