Rust: give more options for building in README.md

Author: redsun82

rust/README.md

@@ -11,10 +11,18 @@ If you don't have the `semmle-code` repo you may need to install Bazel manually,
 
 ### Building the Rust Extractor
 
-This approach uses a released `codeql` version and is simpler to use for QL development. From your `semmle-code` directory run:
+This approach uses a released `codeql` version and is simpler to use for QL development. From anywhere under your `semmle-code` or `codeql` directory you can run:
 ```bash
 bazel run @codeql//rust:install
 ```
+
+You can use shorter versions of the above command:
+```bash
+bazel run //rust:install  # if under the `codeql` checkout
+bazel run rust:install  # if at the root of the `codeql` checkout
+bazel run :install  # if at the `rust` directory of the `codeql` checkout
+```
+
 You now need to create a [per-user CodeQL configuration file](https://docs.github.com/en/code-security/codeql-cli/using-the-advanced-functionality-of-the-codeql-cli/specifying-command-options-in-a-codeql-configuration-file#using-a-codeql-configuration-file) and specify the option:
 ```
 --search-path PATH/TO/semmle-code/ql