build: configure onDemand for release-please

Author: chingor13

.github/release-please.yml

@@ -2,20 +2,29 @@ primaryBranch: main
 releaseType: java-yoshi
 manifest: true
 handleGHRelease: true
+onDemand: true
 branches:
     - branch: 1.0.x
       releaseType: java-backport
       bumpMinorPreMajor: true
+      onDemand: true
     - branch: 1.13.x
       releaseType: java-backport
+      onDemand: true
     - branch: 1.25.x
       releaseType: java-backport
+      onDemand: true
     - branch: 1.37.x
       releaseType: java-backport
+      onDemand: true
     - branch: 1.53.x
       releaseType: java-backport
+      onDemand: true
     - branch: 1.61.x
       releaseType: java-backport
+      onDemand: true
     - branch: 1.58.x
       releaseType: java-backport
+      onDemand: true
     - branch: protobuf-4.x-rc
+      onDemand: true

.github/workflows/sdk-platform-java-sonar.yaml

@@ -47,12 +47,16 @@ jobs:
           key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}
           restore-keys: ${{ runner.os }}-m2
       - name: Install modules to local maven
-        run: |
-          mvn install -T 1C -DskipTests -ntp -B
-          cd java-showcase
-          mvn install -T 1C -DskipTests -ntp -B
+        shell: bash
+        run: .kokoro/build.sh
+        env:
+          BUILD_SUBDIR: sdk-platform-java
+          JOB_TYPE: install
+      - name: Install showcase to local maven
+        run: mvn install -T 1C -DskipTests -ntp -B
+        working-directory: sdk-platform-java/java-showcase
       - name: Parse showcase version
-        working-directory: java-showcase/gapic-showcase
+        working-directory: sdk-platform-java/java-showcase/gapic-showcase
         run: echo "SHOWCASE_VERSION=$(mvn help:evaluate -Dexpression=gapic-showcase.version -q -DforceStdout)" >> "$GITHUB_ENV"
       - name: Install showcase server
         run: |