[SYCLomatic] Add note about LLVM_PARALLEL_LINK_JOBS (#768)

Signed-off-by: Cai, Justin <[email protected]>

Author: jzc

README.md

@@ -101,7 +101,8 @@ cmake -G Ninja -DCMAKE_INSTALL_PREFIX=%PATH_TO_C2S_INSTALL_FOLDER%  -DCMAKE_BUIL
 ninja install-c2s
 ```
 
-Note: For build system with 16G or less memory, recommend to use less than 5 threads for compilation, you may meet out of memory issue when more than 4 threads used for compilation.
+Note: For build system with 16G or less memory, to avoid out of memory issues,
+it is recommended to add the option `-DLLVM_PARALLEL_LINK_JOBS=1` in the CMake step and use 4 or less total parallel jobs when building SYCLomatic by invoking `ninja` with the option `-j4`:
 ```
 ninja -j4 install-c2s
 ```