[clang][flang] Moke the definition of -module-dir restricted to Flang

`-module-dir` is a Flang specific option and should not be visible in
Clang. This patch adds `FlangOnlyOption` flag to its definition. This
way Clang will know that it should reject it and skip it when generating
output for `clang -help`.

The definition of `-module-dir` is moved next to other Flang options.
As `-J` is an alias for `-module-dir`, it has to be moved as well (the
alias cannot be defined before the original option). As `gfortran` mode
is effectively no longer supported (*), `-J` is claimed as Flang only
option.

This is a follow-up of a post-commit review for
https://reviews.llvm.org/D95448.

* https://reviews.llvm.org/rG6a75496836ea14bcfd2f4b59d35a1cad4ac58cee

Differential Revision: https://reviews.llvm.org/D99018

Author: banach-space

clang/include/clang/Driver/Options.td

@@ -986,11 +986,6 @@ def dependency_dot : Separate<["-"], "dependency-dot">, Flags<[CC1Option]>,
 def module_dependency_dir : Separate<["-"], "module-dependency-dir">,
   Flags<[CC1Option]>, HelpText<"Directory to dump module dependencies to">,
   MarshallingInfoString<DependencyOutputOpts<"ModuleDependencyOutputDir">>;
-def module_dir : Separate<["-"], "module-dir">, Flags<[FlangOption,FC1Option]>, MetaVarName<"<dir>">,
-  HelpText<"Put MODULE files in <dir>">,
-  DocBrief<[{This option specifies where to put .mod files for compiled modules.
-It is also added to the list of directories to be searched by an USE statement.
-The default is the current directory.}]>;
 def dsym_dir : JoinedOrSeparate<["-"], "dsym-dir">,
   Flags<[NoXarchOption, RenderAsInput]>,
   HelpText<"Directory to output dSYM's (if any) to">, MetaVarName<"<dir>">;
@@ -4220,7 +4215,6 @@ defm devirtualize_speculatively : BooleanFFlag<"devirtualize-speculatively">,
 
 // Generic gfortran options.
 def A_DASH : Joined<["-"], "A-">, Group<gfortran_Group>;
-def J : JoinedOrSeparate<["-"], "J">, Flags<[RenderJoined,FlangOption,FC1Option]>, Group<gfortran_Group>, Alias<module_dir>;
 def cpp : Flag<["-"], "cpp">, Group<gfortran_Group>;
 def nocpp : Flag<["-"], "nocpp">, Group<gfortran_Group>;
 def static_libgfortran : Flag<["-"], "static-libgfortran">, Group<gfortran_Group>;
@@ -4303,6 +4297,12 @@ def Xflang : Separate<["-"], "Xflang">,
 //===----------------------------------------------------------------------===//
 let Flags = [FC1Option, FlangOption, FlangOnlyOption] in {
 
+def module_dir : Separate<["-"], "module-dir">, MetaVarName<"<dir>">,
+  HelpText<"Put MODULE files in <dir>">,
+  DocBrief<[{This option specifies where to put .mod files for compiled modules.
+It is also added to the list of directories to be searched by an USE statement.
+The default is the current directory.}]>;
+
 def ffixed_form : Flag<["-"], "ffixed-form">, Group<f_Group>,
   HelpText<"Process source files in fixed form">;
 def ffree_form : Flag<["-"], "ffree-form">, Group<f_Group>,
@@ -4340,6 +4340,11 @@ def falternative_parameter_statement : Flag<["-"], "falternative-parameter-state
   HelpText<"Enable the old style PARAMETER statement">;
 }
 
+def J : JoinedOrSeparate<["-"], "J">,
+  Flags<[RenderJoined, FlangOption, FC1Option, FlangOnlyOption]>,
+  Group<gfortran_Group>,
+  Alias<module_dir>;
+
 //===----------------------------------------------------------------------===//
 // FC1 Options
 //===----------------------------------------------------------------------===//