memfd_create on android api level 30 and above

[madushan1000]

Looks like this function is now available in android libc for api level 30 and above. check the bionic libc status docs. There are few other functions listed there too but this is the only one I tested by building a rust program against the latest ndk(r26c).
prototype is

pub fn memfd_create(name: *const ::c_char, flags: ::c_uint) -> ::c_int;