remove the last changing file from cache

Author: matklad

.travis.yml

@@ -2,6 +2,7 @@ cache: cargo
 before_cache:
   - find ./target/debug -type f -maxdepth 1 -delete
   - rm -fr ./target/debug/{deps,.fingerprint}/{*ra_*,*test*,*tools*,*gen_lsp*}
+  - rm -f  ./target/.rustc_info.json
 
 env:
   - CARGO_INCREMENTAL=0