[libc++] Fixes the Clang modular build.

The patch
430b397 ("[libc++] Granularize <type_traits> includes in <iterator>") missed some exports in the modulemap with became apparent in the reverting commit 12cb1cb.

This fixes the issue by updating the modulemap. Note that the Clang ICE is not fixed by this change.

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D142690

(cherry picked from commit a7f8ddc)

Author: mordante

libcxx/include/module.modulemap.in

@@ -755,13 +755,19 @@ module std [system] {
       module derived_from               { private header "__concepts/derived_from.h" }
       module destructible               { private header "__concepts/destructible.h" }
       module different_from             { private header "__concepts/different_from.h" }
-      module equality_comparable        { private header "__concepts/equality_comparable.h" }
+      module equality_comparable {
+        private header "__concepts/equality_comparable.h"
+        export type_traits.common_reference
+      }
       module invocable                  { private header "__concepts/invocable.h" }
       module movable                    { private header "__concepts/movable.h" }
       module predicate                  { private header "__concepts/predicate.h" }
       module regular                    { private header "__concepts/regular.h" }
       module relation                   { private header "__concepts/relation.h" }
-      module same_as                    { private header "__concepts/same_as.h" }
+      module same_as {
+        private header "__concepts/same_as.h"
+        export type_traits.is_same
+      }
       module semiregular                { private header "__concepts/semiregular.h" }
       module swappable                  { private header "__concepts/swappable.h" }
       module totally_ordered            { private header "__concepts/totally_ordered.h" }
@@ -979,7 +985,11 @@ module std [system] {
       module back_insert_iterator  { private header "__iterator/back_insert_iterator.h" }
       module bounded_iter          { private header "__iterator/bounded_iter.h" }
       module common_iterator       { private header "__iterator/common_iterator.h" }
-      module concepts              { private header "__iterator/concepts.h" }
+      module concepts {
+        private header "__iterator/concepts.h"
+        export concepts.equality_comparable
+        export type_traits.common_reference
+      }
       module counted_iterator      { private header "__iterator/counted_iterator.h" }
       module data                  { private header "__iterator/data.h" }
       module default_sentinel      { private header "__iterator/default_sentinel.h" }