Revert "[clang-tools-extra] fix the check for if '-latomic' is necessary"

This reverts commit 1d40c41.
This seemed to have caused build failures on ARM/AArch64.

Author: luismarques

clang-tools-extra/clangd/CMakeLists.txt

@@ -30,7 +30,7 @@ if(CLANG_BUILT_STANDALONE)
 endif()
 
 set(CLANGD_ATOMIC_LIB "")
-if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB OR NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB)
+if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB)
   list(APPEND CLANGD_ATOMIC_LIB "atomic")
 endif()