[llvm] On Windows, in the release build script, fix detecting if clang-cl is in PATH (PR #149597)

[Alexandre Ganea via llvm-commits]

https://github.com/aganea created https://github.com/llvm/llvm-project/pull/149597

The checks for detecting if `clang-cl` and `lld-link` are in `%PATH` were wrong.

This fixes the comment in https://github.com/llvm/llvm-project/pull/135446#discussion_r2215511129

>From 0a33f92daa17107ed00861e2c8e7fc71803b6fe0 Mon Sep 17 00:00:00 2001
From: Alexandre Ganea <aganea at havenstudios.com>
Date: Fri, 18 Jul 2025 17:29:59 -0400
Subject: [PATCH] Fix ERRORELEVEL check when detecting if clang-cl is in PATH

---
 llvm/utils/release/build_llvm_release.bat | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/utils/release/build_llvm_release.bat b/llvm/utils/release/build_llvm_release.bat
index 3042fc2d77dd1..54645d0c6369f 100755
--- a/llvm/utils/release/build_llvm_release.bat
+++ b/llvm/utils/release/build_llvm_release.bat
@@ -169,9 +169,9 @@ set common_cmake_flags=^
 
 if "%force-msvc%" == "" (
   where /q clang-cl
-  if errorlevel 0 (
+  if %errorlevel% EQU 0 (
     where /q lld-link
-    if errorlevel 0 (
+    if %errorlevel% EQU 0 (
       set common_compiler_flags=%common_compiler_flags% -fuse-ld=lld
       
       set common_cmake_flags=%common_cmake_flags%^