__USE_POSIX and VS Code in WSL distro

I'm learning C and in general I code with VS Code in Ubuntu. For convenience, I'm trying to migrate my learning materials to Windows where a lot of my other works happen, so I installed WSL 2 and its distro Ubuntu 18.04 LTS. After installing VS Code for Windows and its remote extension to work with WSL, I boot up a new WSL session in VS Code, install the C/C++ extension with IntelliSense then write a simple program like below just for demonstration:

#include 

int main()
{
    kill(-1, SIGKILL);
}

The problem with VS Code is that while the program compiles, its IntelliSense doesn't detect the kill function in the signal.h header. By further investigating the header file, I observe that the following part is darkened

#ifdef __USE_POSIX
extern int kill (__pid_t __pid, int __sig) __THROW;
#endif /* Use POSIX.  */

along with other parts where __USE_POSIX is checked, including but not limited to siginfo_t, struct sigaction. Is there a way to make VS Code recognise these macros/variables to enable IntelliSense's assistance?