Set SOURCE_DATE_EPOCH later, it casuses some test failures

Author: stefanor

.github/workflows/reusable-ubuntu.yml

@@ -70,8 +70,6 @@ jobs:
         # On ubuntu-26.04 image, LLVM is LLVM-21 by default
         sudo apt-get install --no-install-recommends bolt-21
         echo PATH="$(llvm-config-21 --bindir):$PATH" >> $GITHUB_ENV
-    - name: Use the commit timestamp for timestamps the install
-      run: echo "SOURCE_DATE_EPOCH=$(git log -1 --format=%ct)" >> $GITHUB_ENV
     - name: Configure OpenSSL env vars
       run: |
         echo "MULTISSL_DIR=${GITHUB_WORKSPACE}/multissl" >> "$GITHUB_ENV"
@@ -140,6 +138,9 @@ jobs:
       run: xvfb-run make ci EXTRATESTOPTS="${TEST_OPTS}"
       env:
         TEST_OPTS: ${{ inputs.test-opts }}
+    - name: Use the commit timestamp for timestamps the install
+      if: inputs.upload-install-hashes
+      run: echo "SOURCE_DATE_EPOCH=$(git log -1 --format=%ct)" >> $GITHUB_ENV
     - name: Install Python
       if: inputs.upload-install-hashes
       working-directory: ${{ env.CPYTHON_BUILDDIR }}