Update CMakeLists.txt for better debug info

[JinjieZhao]

Add -fstandalone-debug to emit full debug info

[skyzh]

do you have any comparison on the debug information produced before and after this option is enabled? i.e., do you see more information in your debugger?

[JinjieZhao]

Without -fstandalone-debug p str -> error: summary string parsing error With -fstandalone-debug

[skyzh]

Hmm. This is weird as the debug info should be already embedded in the executable file? I assume the flag only helps generating some debug symbol files outside the executable.

[JinjieZhao]

Yes, it is weird.

For gcc, this flag helps generating some debug symbol files outside the executable. For clang, this flag adds more debug info in the executable. see https://clang.llvm.org/docs/UsersManual.html#controlling-debug-information

[prashanthduvvada]

the '-fstandalone-debug' flag doesn't exist in g++. The g++ does all the prints that clang with '-fstandalone-debug' does by default.

The fix isn't correct. It requires a check if it's g++ or clang.