make MINIOS fails with the following "error: no include path in which to search for stdint.h"

[Acidguy]

Using Ubuntu 20.04 server
the make MINIOS fails with the following "error: no include path in which to search for stdint.h"

super@ubuntu:~/clickosdev/clickos$ make minios
make[1]: Entering directory '/home/super/clickosdev/clickos/minios'

    ____ _ _      _     ___  ____
   / ___| (_) ___| | __/ _ \/ ___|
  | |   | | |/ __| |/ / | | \___ \
  | |___| | | (__|   <| |_| |___) |
   \____|_|_|\___|_|\_\\___/|____/
                                      v0.1

MK /home/super/clickosdev/clickos/minios/build/clickos_x86_64.gz
make[2]: Entering directory '/home/super/clickosdev/clickos/minios'
CC /home/super/clickosdev/mini-os/arch/x86/ioremap.c
In file included from /home/super/clickosdev/mini-os/include/types.h:52,
from /home/super/clickosdev/mini-os/arch/x86/ioremap.c:24:
/usr/lib/gcc/x86_64-linux-gnu/9/include/stdint.h:9:26: error: no include path in which to search for stdint.h
9 | # include_next <stdint.h>
| ^
In file included from /home/super/clickosdev/mini-os/arch/x86/ioremap.c:24:
/home/super/clickosdev/mini-os/include/types.h:79:9: error: unknown type name ‘intptr_t’
79 | typedef intptr_t ptrdiff_t;
| ^~~~~~~~
Any idea how to proceed ?