[compiler-rt] [compiler-rt][www] replace deprecated LLVM_CONFIG_PATH with LLVM_CMAKE_DIR (PR #71500)

[Vitaly Buka via llvm-commits]

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@@ -123,7 +123,7 @@ <h2>Get it and get involved!</h2>
   <li>cd llvm-project</li>
   <li>mkdir build-compiler-rt</li>
   <li>cd build-compiler-rt</li>
-  <li>cmake ../compiler-rt -DLLVM_CONFIG_PATH=/path/to/llvm-config</li>
+  <li>cmake ../compiler-rt -DLLVM_CMAKE_DIR=/path/to/llvm-project/cmake/modules</li>
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vitalybuka wrote:

It does not work `-DCOMPILER_RT_INCLUDE_TESTS=ON` (which I guess default):
-- Builtin supported architectures: 
CMake Error at test/CMakeLists.txt:47 (umbrella_lit_testsuite_begin):
  Unknown CMake command "umbrella_lit_testsuite_begin".

but work with `-DCOMPILER_RT_INCLUDE_TESTS=OFF`

https://github.com/llvm/llvm-project/pull/71500