Always specify cargo toolchain

By always specifying a cargo toolchain (the +${TOOLCHAIN} option) we
avoid being affected by rust-toolchain(.toml) files. Fixes #31.

Author: fornwall

.github/workflows/ci.yml

@@ -33,6 +33,7 @@ jobs:
         # Run twice to test problem with expression caching
         ./tests/scripts/test-runner.sh
         ./tests/scripts/test-runner.sh
+        (cd tests/scripts/ignores-rust-toolchain && ../../../target/debug/rust-script test.rs)
 
   check-format:
     runs-on: ubuntu-latest

tests/scripts/ignores-rust-toolchain/rust-toolchain

@@ -0,0 +1 @@
+invalid-rust-version

tests/scripts/ignores-rust-toolchain/test.rs

@@ -0,0 +1 @@
+std::process::exit(0);