[libc++] Remove a few GCC workarounds that aren't needed anymore (#156290)

Author: philnik777

libcxx/test/std/iterators/iterator.requirements/indirectcallable/indirectinvocable/indirect_result_t.compile.pass.cpp

@@ -34,8 +34,6 @@ static_assert(!has_indirect_result<int, int*>);         // int isn't invocable
 
 // Test ADL-proofing (P2538R1)
 #if TEST_STD_VER >= 26 || defined(_LIBCPP_VERSION)
-// TODO: Enable this on GCC once this bug is fixed: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111419
-#ifndef TEST_COMPILER_GCC
 struct Incomplete;
 template<class T> struct Holder { T t; };
 static_assert(std::same_as<std::indirect_result_t<int                (&)(int), int*>, int>);
@@ -45,4 +43,3 @@ static_assert(std::same_as<std::indirect_result_t<int                (&)(Holder<
 static_assert(std::same_as<std::indirect_result_t<Holder<Incomplete>&(&)(Holder<Incomplete>*), Holder<Incomplete>**>, Holder<Incomplete>&>);
 static_assert(std::same_as<std::indirect_result_t<Holder<Incomplete>*(&)(Holder<Incomplete>*), Holder<Incomplete>**>, Holder<Incomplete>*>);
 #endif
-#endif

libcxx/test/std/utilities/memory/specialized.algorithms/specialized.destroy/ranges_destroy_at.pass.cpp

@@ -52,10 +52,7 @@ struct VirtualCountedBase {
 
 struct VirtualCountedDerived : VirtualCountedBase {
   constexpr VirtualCountedDerived(int& count_ref) : VirtualCountedBase(count_ref) {}
-
-  // Without a definition, GCC gives an error when the destructor is invoked in a constexpr context (see
-  // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93413).
-  constexpr ~VirtualCountedDerived() override {}
+  constexpr ~VirtualCountedDerived() override = default;
 };
 
 constexpr bool test() {

libcxx/test/std/utilities/meta/meta.rel/is_convertible.pass.cpp

@@ -117,12 +117,9 @@ int main(int, char**)
 
     // Non-referencable function type
     static_assert((!std::is_convertible<ConstFunction, Function>::value), "");
-// TODO(LLVM-19): Re-enable this once we switch to GCC 14. This is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109680
-#ifndef TEST_COMPILER_GCC
     static_assert((!std::is_convertible<ConstFunction, Function*>::value), "");
     static_assert((!std::is_convertible<ConstFunction, Function&>::value), "");
     static_assert((!std::is_convertible<ConstFunction, Function&&>::value), "");
-#endif
     static_assert((!std::is_convertible<Function*, ConstFunction>::value), "");
     static_assert((!std::is_convertible<Function&, ConstFunction>::value), "");
     static_assert((!std::is_convertible<ConstFunction, ConstFunction>::value), "");