leanc doesn't find standard c headers

Stream: lean4

[Horatiu Cheval]

I noticed that after setting the default toolchain nightly-2021-12-10 leanc doesn't find the standard c library headers.
If I run leanc main.c where main.c is

#include <stdio.h>

int main(){
    printf("Hello world\n");
}

I get

main.c:1:10: fatal error: 'stdio.h' file not found
#include <stdio.h>
         ^~~~~~~~~
1 error generated.

It works fine if I switch the default toolchain to something nightly-2021-11-24 for instance.
Does anyoane know what might be the cause?