ci,os: fix bootstrapping with -os cross -o vc/v.c (avoid the generic calls in the new write_u8 and read_u8)

vlib/os/file_le_be.c.v

@@ -57,13 +57,17 @@ pub fn (mut f File) read_be[T]() !T {
 // write_u8 writes a single byte value to the file `f`.
 // Note: if possible, use some of the other APIs, that write larger chunks of data, before using write_u8/1.
 pub fn (mut f File) write_u8(b u8) ! {
-	return f.write_le[u8](b)
+	C.errno = 0 // needed for tcc
+	check_fwrite(C.fwrite(voidptr(&b), 1, 1, f.cfile))!
 }
 
 // read_u8 reads a single byte value from the file `f`.
 // Note: if possible, use some of the other APIs, that read larger chunks of data, before using read_u8/1.
 pub fn (mut f File) read_u8() !u8 {
-	return f.read_le[u8]()
+	mut res := u8(0)
+	C.errno = 0 // needed for tcc
+	check_fread(C.fread(voidptr(&res), 1, 1, f.cfile))!
+	return res
 }
 
 // private helpers