Merge #1737

1737: Add  support for feature check. r=CohenArthur a=TuringKi

This commit implements a very basic feature checking module.

The results like this:

```

../gcc/testsuite/rust/compile/feature.rs:1:12: error: unknown feature 'AA'
    1 | #![feature(AA)] //{ dg-error "unknown feature 'AA'" }
      |            ^

```

This commit is split from pr https://github.com/Rust-GCC/gccrs/pull/1718.

Signed-off-by: Xiao Ma <mxlol233@outlook.com>
Co-authored-by: mxlol233 <mxlol233@outlook.com>

diff --cc gcc/rust/Make-lang.in
Simple merge