[llvm] Add `LLVM_BINUTILS_INCDIR` into `LLVM-related variables`. (PR #123342)

[via llvm-commits]

https://github.com/Hammerklavier-cn updated https://github.com/llvm/llvm-project/pull/123342

>From 5e38cded980a3265fe38f0a1004a5c23cad192c7 Mon Sep 17 00:00:00 2001
From: hammerklavier <hammerklavier at noreply.gitcode.com>
Date: Fri, 17 Jan 2025 21:18:10 +0800
Subject: [PATCH] Add `LLVM_BINUTILS_INCDIR` into `LLVM-related variables`.

- As `LLVM_BINUTILS_INCDIR` is essential for compiling LLVMgold.so, I think it is worth being added into the manual.
---
 llvm/docs/CMake.rst | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/llvm/docs/CMake.rst b/llvm/docs/CMake.rst
index 91e34781ef307e..475b580d08befe 100644
--- a/llvm/docs/CMake.rst
+++ b/llvm/docs/CMake.rst
@@ -595,6 +595,13 @@ enabled sub-projects. Nearly all of these variable names begin with
     should only appear in one of the two lists. If a project is a valid possiblity
     for both, prefer putting it in ``LLVM_ENABLE_RUNTIMES``.
 
+**LLVM_BINUTILS_INCDIR**:STRING
+  Specify the path to the directory of `/path/to/binutils/include`,  which contains
+  `plugin-api.h`. This is necessary if you need to integrate binutils tools（like
+  the gold linker) into your LLVM build process even if `plugin-api.h` locates in
+  `/usr/include`. You should also specify this parameter if you want to compile
+  `LLVMgold.so`.
+
 **LLVM_ENABLE_RTTI**:BOOL
   Build LLVM with run-time type information. Defaults to OFF.