ci: cache datadog-ci (#9702)

.github/actions/upload-datadog/action.yaml

@@ -1,4 +1,4 @@
-name: Upload tests to datadog
+name: Upload tests to Datadog
 if: always()
 inputs:
   api-key:
@@ -7,8 +7,26 @@ inputs:
 runs:
   using: "composite"
   steps:
+    - name: Set work dir
+      shell: bash
+      run: |
+        WORK_DIR=${{ runner.temp }}/datadog-ci
+        mkdir -p $WORK_DIR
+        echo "WORK_DIR=$WORK_DIR" >> $GITHUB_ENV
+    # The npm install was taking 30s to 1m, accounting for 20+% of the total
+    # job time.
+    - name: Cache datadog-ci
+      uses: buildjet/cache@v3
+      with:
+        path: |
+          ${{ env.WORK_DIR }}
+        key: datadog-ci-${{ runner.os }}
+        restore-keys: |
+          datadog-ci-${{ runner.os }}-
+          datadog-ci-
     - shell: bash
       run: |
+        cd ${{ env.WORK_DIR }}
         owner=${{ github.repository_owner	 }}
         echo "owner: $owner"
         if [[  $owner != "coder" ]]; then
@@ -20,8 +38,8 @@ runs:
           echo "No API key provided, skipping..."
           exit 0
         fi
-        npm install -g @datadog/datadog-ci@2.10.0
-        datadog-ci junit upload --service coder ./gotests.xml \
+        npm install @datadog/datadog-ci@2.10.0
+        npm x -- datadog-ci junit upload --service coder ./gotests.xml \
           --tags os:${{runner.os}} --tags runner_name:${{runner.name}}
       env:
         DATADOG_API_KEY: ${{ inputs.api-key }}