Revert "[LLVM] Silence compiler-rt warning in runtimes build (#99525)"

Summary:
This patch broke LLVM Flang build on Windows. PR #100202
This reverts commit f6f88f4.

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Differential Revision: https://phabricator.intern.facebook.com/D60250542

llvm/cmake/modules/LLVMExternalProjectUtils.cmake

@@ -350,7 +350,6 @@ function(llvm_ExternalProject_Add name source_dir)
                ${sysroot_arg}
                -DLLVM_BINARY_DIR=${PROJECT_BINARY_DIR}
                -DLLVM_CONFIG_PATH=${llvm_config_path}
-               -DLLVM_CMAKE_DIR=${LLVM_CMAKE_DIR}
                -DLLVM_ENABLE_WERROR=${LLVM_ENABLE_WERROR}
                -DLLVM_HOST_TRIPLE=${LLVM_HOST_TRIPLE}
                -DLLVM_HAVE_LINK_VERSION_SCRIPT=${LLVM_HAVE_LINK_VERSION_SCRIPT}