Disallow warnings when compiling test data (#1623)

Make the test-data compilation binaries reject Cairo warnings so that
`make compile-test-data` fails fast on issues like unused variables.
Fix the three existing offenders by prefixing unused bindings with `_`.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: TomerStarkware

test_data/programs/array_slice_overflow.cairo

@@ -1,4 +1,4 @@
 fn run_test(user_len: u32) {
     let arr: Array<u64> = array![10_u64, 20_u64];
-    let slice = arr.span().slice(1, user_len);
+    let _slice = arr.span().slice(1, user_len);
 }

test_data/programs/libfuncs/array_snapshot_pop_back_clone_offset.cairo

@@ -3,7 +3,7 @@ fn run_test() -> Span<felt252> {
     let mut data = data.span();
 
     assert(*data.pop_front().unwrap() == 7, 0);
-    let data2 = data.clone();
+    let _data2 = data.clone();
 
     assert(*data.pop_back().unwrap() == 193827, 1);
 

test_data/programs/libfuncs/array_snapshot_pop_front_clone_offset.cairo

@@ -3,7 +3,7 @@ fn run_test() -> Span<felt252> {
     let mut data = data.span();
 
     assert(*data.pop_front().unwrap() == 7, 0);
-    let data2 = data.clone();
+    let _data2 = data.clone();
 
     assert(*data.pop_front().unwrap() == 3, 1);
 

test_utils/src/bin/compile-cairo-project.rs

@@ -35,9 +35,7 @@ fn main() -> Result<(), Box<dyn Error>> {
         dbb.build()?
     };
     let crate_inputs = setup_project(&mut db, &args.cairo_path)?;
-    let diagnostics_reporter = DiagnosticsReporter::stderr()
-        .with_crates(&crate_inputs)
-        .allow_warnings();
+    let diagnostics_reporter = DiagnosticsReporter::stderr().with_crates(&crate_inputs);
     let crate_ids = CrateInput::into_crate_ids(&db, crate_inputs);
 
     let program = compile_prepared_db_program_artifact(

test_utils/src/bin/compile-cairo-tests.rs

@@ -22,7 +22,7 @@ fn main() -> Result<(), Box<dyn Error>> {
 
     let compiler = TestCompiler::try_new(
         &args.cairo_path,
-        true,
+        false,
         true,
         TestsCompilationConfig {
             starknet: args.starknet,