[libc++][Modules] Fix a few module related warnings

[iana]

Summary

I'm getting a few -Wundefined-inline warnings, and a -Wnon-modular-include-in-module too. Fix all of those.

[iana]

An example warning I'm hitting locally:

In module 'std_private_algorithm_copy_n' imported from /.../usr/include/c++/v1/__string/char_traits.h:12:
/.../usr/include/c++/v1/__algorithm/copy_n.h:57:1: warning: inline function 'std::copy_n<const char *, unsigned long, char *>' is not defined [-Wundefined-inline]
copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
^
/.../usr/include/c++/v1/__string/char_traits.h:242:14: note: used here
        std::copy_n(__s2, __n, __s1);
             ^

The only way I could find to fix that warning was to make the std_private_string_char_traits module export *.

[iana]

Add a missing include to pstl_sort

[iana]

I can't reproduce the warning in check-cxx or run-buildbot generic-modules and I don't know why. It looks like the tests have -Werror=all, and just in case I tried adding -Werror=undefined-inline, but they still come up green. So I'm stumped why this seems to only reproduce when I install libc++ into my macOS SDK, but it seems like a serious problem with an easy fix that we'd better put into llvm 17.

[Mordante]

In D156508#4544074, @iana wrote:

I can't reproduce the warning in check-cxx or run-buildbot generic-modules and I don't know why. It looks like the tests have -Werror=all, and just in case I tried adding -Werror=undefined-inline, but they still come up green. So I'm stumped why this seems to only reproduce when I install libc++ into my macOS SDK, but it seems like a serious problem with an easy fix that we'd better put into llvm 17.

I think the changes are not too intrusive for LLVM-17 so I'm fine with backporting it.
LGTM!

libcxx/include/module.modulemap.in

 module std_private_algorithm_pstl_frontend_dispatch                      [system] {
   header "__algorithm/pstl_frontend_dispatch.h"
   export std_private_utility_forward
 }
 module std_private_algorithm_pstl_generate                               [system] { header "__algorithm/pstl_generate.h" }
 module std_private_algorithm_pstl_is_partitioned                         [system] { header "__algorithm/pstl_is_partitioned.h" }
 module std_private_algorithm_pstl_merge                                  [system] { header "__algorithm/pstl_merge.h" }
 module std_private_algorithm_pstl_replace                                [system] { header "__algorithm/pstl_replace.h" }
+module std_private_algorithm_pstl_sort                                   [system] { header "__algorithm/pstl_sort.h" }
 module std_private_algorithm_pstl_stable_sort                            [system] {
   header "__algorithm/pstl_stable_sort.h"
   export std_private_functional_operations
 }
 module std_private_algorithm_pstl_transform                              [system] { header "__algorithm/pstl_transform.h" }
 module std_private_algorithm_push_heap                                   [system] { header "__algorithm/push_heap.h" }
 module std_private_algorithm_ranges_adjacent_find                        [system] { header "__algorithm/ranges_adjacent_find.h" }
 module std_private_algorithm_ranges_all_of                               [system] { header "__algorithm/ranges_all_of.h" }

 module std_private_memory_allocate_at_least               [system] { header "__memory/allocate_at_least.h" }
 module std_private_memory_allocation_guard                [system] { header "__memory/allocation_guard.h" }
 module std_private_memory_allocator                       [system] { header "__memory/allocator.h" }
 module std_private_memory_allocator_arg_t                 [system] { header "__memory/allocator_arg_t.h" }
 module std_private_memory_allocator_destructor            [system] { header "__memory/allocator_destructor.h" }
 module std_private_memory_allocator_traits                [system] { header "__memory/allocator_traits.h" }
 module std_private_memory_assume_aligned                  [system] { header "__memory/assume_aligned.h" }
 module std_private_memory_auto_ptr                        [system] { header "__memory/auto_ptr.h" }
-module std_private_memory_builtin_new_allocator           [system] { header "__memory/builtin_new_allocator.h" }
+module std_private_memory_builtin_new_allocator           [system] {
+  header "__memory/builtin_new_allocator.h"
+  export *
+}
 module std_private_memory_compressed_pair                 [system] { header "__memory/compressed_pair.h" }
 module std_private_memory_concepts                        [system] {
   header "__memory/concepts.h"
   export std_private_type_traits_remove_reference
 }
 module std_private_memory_construct_at                    [system] { header "__memory/construct_at.h" }
 module std_private_memory_destruct_n                      [system] { header "__memory/destruct_n.h" }
 module std_private_memory_pointer_traits                  [system] { header "__memory/pointer_traits.h" }
module std_private_random_piecewise_constant_distribution [system] {
   header "__random/piecewise_constant_distribution.h"
   export *
 }
 module std_private_random_piecewise_linear_distribution   [system] {
   header "__random/piecewise_linear_distribution.h"
   export *
 }
 module std_private_random_poisson_distribution            [system] { header "__random/poisson_distribution.h" }
-module std_private_random_random_device                   [system] { header "__random/random_device.h" }
+module std_private_random_random_device                   [system] {
+  header "__random/random_device.h"
+  export *
+}
 module std_private_random_ranlux                          [system] { header "__random/ranlux.h" }
-module std_private_random_seed_seq                        [system] { header "__random/seed_seq.h" }
+module std_private_random_seed_seq                        [system] {
+  header "__random/seed_seq.h"
+  export *
+}
 module std_private_random_shuffle_order_engine            [system] { header "__random/shuffle_order_engine.h" }
 module std_private_random_student_t_distribution          [system] { header "__random/student_t_distribution.h" }
 module std_private_random_subtract_with_carry_engine      [system] { header "__random/subtract_with_carry_engine.h" }
 module std_private_random_uniform_int_distribution        [system] { header "__random/uniform_int_distribution.h" }
 module std_private_random_uniform_random_bit_generator    [system] { header "__random/uniform_random_bit_generator.h" }
 module std_private_random_uniform_real_distribution       [system] { header "__random/uniform_real_distribution.h" }
 module std_private_random_weibull_distribution            [system] { header "__random/weibull_distribution.h" }
 
module std_private_stop_token_stop_state           [system] {
   header "__stop_token/stop_state.h"
   export *
 }
 module std_private_stop_token_stop_token           [system] {
   header "__stop_token/stop_token.h"
   export *
 }
 
-module std_private_string_char_traits           [system] { header "__string/char_traits.h" }
+module std_private_string_char_traits           [system] {
+  header "__string/char_traits.h"
+  export *
+}
 module std_private_string_constexpr_c_functions [system] {
   header "__string/constexpr_c_functions.h"
   export std_private_type_traits_is_equality_comparable
 }
 module std_private_string_extern_template_lists [system] { header "__string/extern_template_lists.h" }
 module std_private_string_string_fwd            [system] { header "__fwd/string.h" }
 
 module std_private_string_view_string_view_fwd [system] { header "__fwd/string_view.h" }