ci: detect trailing whitespace (#7013)

.github/buildomat/README.md

@@ -12,7 +12,7 @@ reproduce the failure on other operating systems, don't worry! The
 [tokio-rs/illumos] team is responsible for maintaining Tokio's illumos support,
 and can be called on to assist contributors with illumos-specific issues. Please
 feel free to tag @tokio-rs/illumos to ask for help resolving build failures on
-illumos 
+illumos.
 
 [illumos]: https://www.illumos.org/
 [Buildomat]: https://github.com/oxidecomputer/buildomat

.github/workflows/ci.yml

@@ -1103,4 +1103,5 @@ jobs:
           }
       - name: Run cargo-spellcheck
         run: cargo spellcheck --code 1
-
+      - name: Detect trailing whitespace
+        run: if grep --exclude-dir=.git --exclude-dir=target -re '\s$' . ; then exit 1; fi