chore: fallback from nightly if compiler is broken (#12133)

Justfile

@@ -165,12 +165,21 @@ check-protocol-schema:
     rustup toolchain install nightly
     rustup target add wasm32-unknown-unknown --toolchain nightly
 
+    # Below, we *should* have been used `cargo +nightly ...` instead of
+    # `RUSTC_BOOTSTRAP=1`. However, the env var appears to be more stable.
+    # `nightly` builds are updated daily and may be broken sometimes, e.g.
+    # https://github.com/rust-lang/rust/issues/130769.
+    #
+    # If there is an issue with the env var, fall back to `cargo +nightly ...`.
+
     # Test that checker is not broken
-    RUSTFLAGS="--cfg enable_const_type_id" cargo +nightly test -p protocol-schema-check --profile dev-artifacts
+    RUSTC_BOOTSTRAP=1 RUSTFLAGS="--cfg enable_const_type_id" \
+        cargo test -p protocol-schema-check --profile dev-artifacts
+
     # Run the checker
-    RUSTFLAGS="--cfg enable_const_type_id" \
+    RUSTC_BOOTSTRAP=1 RUSTFLAGS="--cfg enable_const_type_id" \
         {{ with_macos_incremental }} \
-        cargo +nightly run -p protocol-schema-check --profile dev-artifacts
+        cargo run -p protocol-schema-check --profile dev-artifacts
 
 check_build_public_libraries:
     cargo check {{public_libraries}}