[Bug ada/81114] GNAT mishandles filenames with UTF8 chars on case-insensitive filesystems

["simon at pushface dot org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81114

--- Comment #3 from simon at pushface dot org ---
Just for interest, this not-very-good code will successfully convert
the uppercase-a-acute input c381 to uppercase-a/combining-acute 41cc81:

#include <stdio.h>
#include <iconv.h>
#include <stdint.h>
#include <memory.h>

int main(void)
{
  uint8_t codepoint[] = {0xc3, 0x81, 0};
  char *input = (char *) &codepoint;
  size_t in_size = 2;

  char output_buffer[10];
  memset(output_buffer, 0, sizeof(output_buffer));
  char *output = output_buffer;
  size_t out_size = 10;

  iconv_t cd = iconv_open("utf8-mac", "UTF-8");

  iconv(cd, &input, &in_size, &output, &out_size);

  printf("in %d out %d result \"%s\"\n", in_size, out_size, output_buffer);

  return 0;
}

but of course only on macOS - https://stackoverflow.com/a/23159081/40851