[clang] [Clang][Docs] Discontinue documenting the GCC -I- and --include-barrier options. (PR #184941)

[Tom Honermann via cfe-commits]

https://github.com/tahonermann created https://github.com/llvm/llvm-project/pull/184941

Clang has never implemented the GCC `-I-` and `--include-barrier` options. An error is issued if they are used. GCC deprecated these options in GCC 4. Advertising their availability in documentation and help text is misleading.

>From 5b44b67fd877003581dd0b21e8421367b16ae45a Mon Sep 17 00:00:00 2001
From: Tom Honermann <tom.honermann at intel.com>
Date: Thu, 5 Mar 2026 18:48:45 -0800
Subject: [PATCH] [Clang][Docs] Discontinue documenting the GCC -I- and
 --include-barrier options.

Clang has never implemented the GCC -I- and --include-barrier options.
An error is issued if they are used. GCC deprecated these options in
GCC 4. Advertising their availability in documentation and help text
is misleading.
---
 clang/include/clang/Options/Options.td | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/clang/include/clang/Options/Options.td b/clang/include/clang/Options/Options.td
index fe7169423b6bf..c71df8e9bdc3b 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -62,7 +62,7 @@ def LinkOption : OptionFlag;
 // target will lead to an err_drv_unsupported_opt_for_target error.
 def TargetSpecific : OptionFlag;
 
-// Indicates that this warning is ignored, but accepted with a warning for
+// Indicates that this option is ignored, but accepted with a warning for
 // GCC compatibility.
 class IgnoredGCCCompat : Flags<[HelpHidden]> {}
 
@@ -784,7 +784,7 @@ def fshow_skipped_includes : Flag<["-"], "fshow-skipped-includes">,
              or #pragma once. This flag makes -H show also such includes.}]>,
   MarshallingInfoFlag<DependencyOutputOpts<"ShowSkippedHeaderIncludes">>;
 
-def I_ : Flag<["-"], "I-">, Group<I_Group>,
+def I_ : Flag<["-"], "I-">, Group<I_Group>, IgnoredGCCCompat,
     HelpText<"Restrict all prior -I flags to double-quoted inclusion and "
              "remove current directory from include path">;
 def I : JoinedOrSeparate<["-"], "I">, Group<I_Group>,