Auto merge of #14126 - eth3lbert:snapbox-rrs, r=epage

test: migrate rustflags, rustup and script to snapbox

### What does this PR try to resolve?

Part of #14039.

Migrate following to snapbox:

- `tests/testsuite/rustflags.rs`
- `tests/testsuite/rustup.rs`
- `tests/testsuite/script.rs`

crates/cargo-test-support/src/compare.rs

@@ -179,6 +179,11 @@ fn add_common_redactions(subs: &mut snapbox::Redactions) {
         regex!(r"home/\.cargo/registry/src/-(?<redacted>[a-z0-9]+)"),
     )
     .unwrap();
+    subs.insert(
+        "[HASH]",
+        regex!(r"\.cargo/target/(?<redacted>[0-9a-f]{2}/[0-9a-f]{14})"),
+    )
+    .unwrap();
     subs.insert("[HASH]", regex!(r"/[a-z0-9\-_]+-(?<redacted>[0-9a-f]{16})"))
         .unwrap();
     subs.insert("[HOST_TARGET]", rustc_host()).unwrap();