avoid fallback logic (and we do not need the flag value currently anyway)

Author: RalfJung

src/shims/posix/linux/foreign_items.rs

@@ -208,11 +208,9 @@ fn getrandom<'tcx>(
 
     // The only supported flags are GRND_RANDOM and GRND_NONBLOCK,
     // neither of which have any effect on our current PRNG.
-    let flags = this.read_scalar(flags)?;
-    // Either `i32` or `isize` is fine.
-    if flags.to_machine_isize(this).is_err() {
-        flags.to_i32()?;
-    }
+    let _flags = this.read_scalar(flags)?;
+    // FIXME: Check that this is an integer type of the right size.
+    // Currently, some callers pass i32 and some usize, is that even allowed?
 
     this.gen_random(ptr, len)?;
     this.write_scalar(Scalar::from_machine_usize(len, this), dest)?;