[objc docs] Fix doc generation workflow

.github/workflows/publish-objectivec-apidocs.yml

@@ -30,9 +30,11 @@ jobs:
     timeout-minutes: 120
     steps:
     - uses: actions/checkout@d23441a48e516b6c34aea4fa41551a30e30af803 # v6.1.0
+
     - name: Get vcpkg tool info
       id: vcpkg-tool-info
       uses: ./.github/actions/get-vcpkg-tool-info
+
     - uses: microsoft/onnxruntime-github-actions/setup-build-tools@d19341fb036c43a947a2c0e4a53ad4d15e10bc5c # v0.0.9
       with:
         vcpkg-version: ${{ steps.vcpkg-tool-info.outputs.release_tag }}
@@ -42,11 +44,14 @@ jobs:
         add-cmake-to-path: 'true'
         disable-terrapin: 'true'
 
-    - name: Install Jazzy
-      run: |
-        sudo gem install jazzy --version 0.14.3
+    - name: Install Jazzy and dependencies
+      env:
+        BUNDLE_GEMFILE: ./objectivec/docs/Gemfile
+      run: bundle install
 
     - name: Generate Objective-C docs
+      env:
+        BUNDLE_GEMFILE: ./objectivec/docs/Gemfile
       run: |
         set -e
 
@@ -56,7 +61,7 @@ jobs:
                "This documentation was generated from the ONNX Runtime source at commit ${ORT_COMMIT_SHORT}." \
                >> ./objectivec/docs/main_page.md
 
-        jazzy --config ./objectivec/docs/jazzy_config.yaml \
+        bundle exec jazzy --config ./objectivec/docs/jazzy_config.yaml \
               --clean --output ./_site/docs/api/objectivec
       shell: bash
 

objectivec/docs/Gemfile

@@ -0,0 +1,4 @@
+source "https://rubygems.org"
+
+gem "jazzy", "0.15.4"
+gem "mustache", "< 1.1.3" # Work around https://github.com/realm/jazzy/issues/1435.

objectivec/docs/readme.md

@@ -4,12 +4,23 @@ The API should be documented with comments in the [public header files](../inclu
 
 ## Documentation Generation
 
+Documentation generation dependencies are defined in [Gemfile](./Gemfile) and managed with
+[Bundler](https://bundler.io/).
+
 The [Jazzy](https://github.com/realm/jazzy) tool is used to generate documentation from the code.
 
-To generate documentation, from the repo root, run:
+To install the dependencies, from the repo root, run:
+
+```bash
+BUNDLE_GEMFILE=objectivec/docs/Gemfile bundle install
+```
+
+Then, to generate the documentation, run:
 
 ```bash
-jazzy --config objectivec/docs/jazzy_config.yaml --output <output directory>
+BUNDLE_GEMFILE=objectivec/docs/Gemfile bundle exec jazzy \
+	--config objectivec/docs/jazzy_config.yaml \
+	--output <output directory>
 ```
 
 The generated documentation website files will be in `<output directory>`.