c2rust-analyze: Add a cargo wrapper (#1036)

* Fixes #709.
* Fixes #708.

This adds an MVP of a `cargo` wrapper for `c2rust-analyze` so that it
can be run on a whole crate like `cargo`. This copies the approach from
`c2rust-instrument`, with some minor adjustments:
* We don't care about the instrumentation and metadata
`c2rust-instrument` need, so that code is gone.
* We still allow `c2rust-analyze` to be called as a `rustc_wrapper`
directly. More specifically, the `cargo` wrapper is supposed to set
`RUST_SYSROOT`. `c2rust-instrument` requires this, while
`c2rust-analyze` will re-calculate it if it wasn't.

This allows us to keep using the `rustc` wrapper in tests,
as the tests are all set up as single files meant to be compiled with
`rustc` directly.
We can change this, but that'll come later. The exception is the
`lighttpd_minimal` and `with_pdg_file` tests, as those run on full
crates. I converted `lighttpd_minimal` to use the `cargo` wrapper as a
proof of concept to show it works. I tried to do the same for
`with_pdg_file`, but it updated some of the hashes or something so now
the PDG binary has out-of-date `DefPathHash`es, and I'm not sure how to
regenerate a new one.

.gitignore

@@ -49,3 +49,4 @@ marks.*.json
 # Outputs of `c2rust-analyze`
 inspect/
 *.analysis.txt
+analysis.txt

analysis/tests/lighttpd-minimal/src/main.rs

@@ -6,8 +6,6 @@
 #![allow(unused_variables)]
 #![feature(extern_types)]
 
-extern crate libc;
-
 use libc::*;
 use std::mem;
 

c2rust-analyze/Cargo.toml

@@ -15,7 +15,7 @@ categories.workspace = true
 polonius-engine = "0.13.0"
 rustc-hash = "1.1.0"
 bitflags = "1.3.2"
-c2rust-pdg = { path = "../pdg"}
+c2rust-pdg = { path = "../pdg" }
 bincode = "1.0"
 serde = "1.0"
 assert_matches = "1.5.0"
@@ -25,6 +25,10 @@ log = "0.4.17"
 backtrace = "0.3.67"
 itertools = "0.10"
 libc = "0.2.147"
+clap = { version = "4.2.7", features = ["derive"] }
+fs-err = "2.9.0"
+anyhow = "1.0.75"
+toml_edit = "0.19.8"
 
 [build-dependencies]
 c2rust-build-paths = { path = "../c2rust-build-paths", version = "0.18.0" }