Update Build Wheels to only build once on RCs (#32009)

.github/workflows/build_wheels.yml

@@ -236,6 +236,7 @@ jobs:
             arch: aarch64
     steps:
     - name: Download python source distribution from artifacts
+      if: ${{ needs.build_source.outputs.is_rc == 0 }}
       # Pinned to v3 because of https://github.com/actions/download-artifact/issues/249
       uses: actions/download-artifact@v3
       with:
@@ -259,6 +260,7 @@ jobs:
       # note: sync cibuildwheel version with gradle task sdks:python:bdistPy* steps
       run: pip install cibuildwheel==2.17.0 setuptools
     - name: Build wheel
+      if: ${{ needs.build_source.outputs.is_rc == 0 }}
       working-directory: apache-beam-source
       env:
         CIBW_BUILD: ${{ matrix.os_python.python }}
@@ -271,13 +273,15 @@ jobs:
       if: startsWith(matrix.os_python.os, 'macos')
       run: brew install coreutils
     - name: Add checksums
+      if: ${{ needs.build_source.outputs.is_rc == 0 }}
       working-directory: apache-beam-source/wheelhouse/
       run: |
         for file in *.whl; do
           sha512sum $file > ${file}.sha512
         done
       shell: bash
     - name: Upload wheels as artifacts
+      if: ${{ needs.build_source.outputs.is_rc == 0 }}
       # Pinned to v3 because of https://github.com/actions/download-artifact/issues/249
       uses: actions/upload-artifact@v3
       with: