[libc++] Add missing <stdbool.h> to the modulemap

It used to be defined by the compiler, but libc++ now provides it.

Differential Revision: https://reviews.llvm.org/D131201

NOKEYCHECK=True
GitOrigin-RevId: 0a5c344a84a452452185f3a6bd7d7679a42abb42
diff --git a/include/module.modulemap.in b/include/module.modulemap.in
index 204fe40..83c6384 100644
--- a/include/module.modulemap.in
+++ b/include/module.modulemap.in
@@ -59,7 +59,10 @@
     // FIXME: <stdalign.h> is missing.
     // <signal.h> provided by C library.
     // <stdarg.h> provided by compiler.
-    // <stdbool.h> provided by compiler.
+    module stdbool_h {
+      // <stdbool.h>'s __bool_true_false_are_defined macro requires textual inclusion.
+      textual header "stdbool.h"
+    }
     module stddef_h {
       // <stddef.h>'s __need_* macros require textual inclusion.
       textual header "stddef.h"