Assistance needed - API access issue

[Kaushal Singh]

Hi,
I hope this message finds you well. I am writing to seek assistance with a 
problem I've encountered while trying to access the grub_util_is_regular API.
We want to use this API to perform a file check while booting.

For example if we want to access grub_util_is_regular  API in file 
"/grub-core/hello/hello.c"
When we use the same API in hello.c file, with inclusion of "#include 
<grub/emu/hostfile.h >" but building getting failed with error
"../include/grub/emu/hostfile.h:24:10: fatal error: sys/types.h: No such file 
or directory"

Please suggest how can we use the API or how can I include std library 
functions, do we not do some changes in our Makefile or something else.

As per the File: /include/grub/emu/hostfile.h
int EXPORT_FUNC(grub_util_is_regular) (const char *path);

Thanks, Kaushal