Rust: add test rust-toolchain.toml after fixing .gitignore

Author: redsun82

rust/ql/test/.gitignore

@@ -2,7 +2,7 @@ target/
 
 # these are all generated, see `rust/extractor/src/qltest.rs` for details
 Cargo.toml
-rust-toolchain.toml
+/*/**/rust-toolchain.toml
 lib.rs
 .proc_macro/
 .lib/

rust/ql/test/rust-toolchain.toml

@@ -0,0 +1,7 @@
+# This file specifies the Rust version used to test the rust extractor.
+# IMPORTANT: this can also have an impact on QL test results
+
+[toolchain]
+channel = "1.86"
+profile = "minimal"
+components = [ "rust-src" ]