[clang][builtins] Add stdckdint.h to the modulemap. (#166230)

All builtin Clang headers need to be covered by the modulemap.

This fixes https://github.com/llvm/llvm-project/issues/166173

clang/lib/Headers/module.modulemap

@@ -253,6 +253,11 @@ module _Builtin_stdbool [system] {
   export *
 }
 
+module _Builtin_stdckdint [system] {
+  header "stdckdint.h"
+  export *
+}
+
 module _Builtin_stdcountof [system] {
   header "stdcountof.h"
   export *

clang/lib/Lex/ModuleMap.cpp

@@ -258,6 +258,7 @@ static bool isBuiltinHeaderName(StringRef FileName) {
            .Case("stdarg.h", true)
            .Case("stdatomic.h", true)
            .Case("stdbool.h", true)
+           .Case("stdckdint.h", true)
            .Case("stdcountof.h", true)
            .Case("stddef.h", true)
            .Case("stdint.h", true)

clang/test/Modules/Inputs/builtin-headers/system-modules.modulemap

@@ -49,6 +49,11 @@ module cstd [system] [no_undeclared_includes] {
     export *
   }
 
+  module stdckdint {
+    header "stdckdint.h"
+    export *
+  }
+
   module stdcountof {
     header "stdcountof.h"
     export *

clang/test/Modules/builtin-headers.mm

@@ -17,6 +17,7 @@
 @import _Builtin_stdarg;
 @import _Builtin_stdatomic;
 @import _Builtin_stdbool;
+@import _Builtin_stdckdint;
 @import _Builtin_stdcountof;
 @import _Builtin_stddef;
 @import _Builtin_stdint;