[compiler-rt][www] Update standalone build instruction (#98707)

Follow up to #71500

compiler-rt/www/index.html

@@ -116,14 +116,13 @@ <h2>Get it and get involved!</h2>
     cmake.
 
   <p>To build it separately, first
-  <a href="https://llvm.org/docs/CMake.html#quick-start">build LLVM</a>
-  separately to get llvm-config binary, and then run:
+  <a href="https://llvm.org/docs/CMake.html#quick-start">build LLVM</a>, and then run:
 
   <ul>
   <li>cd llvm-project</li>
   <li>mkdir build-compiler-rt</li>
   <li>cd build-compiler-rt</li>
-  <li>cmake ../compiler-rt -DLLVM_CMAKE_DIR=/path/to/llvm-project/cmake/modules</li>
+  <li>cmake ../compiler-rt -DLLVM_CMAKE_DIR=/path/to/llvm-build-dir</li>
   <li>make</li>
   </ul>