punctuation

Co-authored-by: Ralf Jung <[email protected]>

Author: jyn514

CONTRIBUTING.md

@@ -144,7 +144,7 @@ The setup for a local rustc works as follows:
 # Clone the rust-lang/rust repo.
 git clone https://github.com/rust-lang/rust rustc
 cd rustc
-# Create a config.toml with defaults for working on miri
+# Create a config.toml with defaults for working on miri.
 ./x.py setup compiler
 
 # Build stage2 rustc using the stage1 compiler.