ci(release-image): Skip setup steps when using persistent BuildKit

When BUILDKIT_ENDPOINT is set, the build happens on a remote BuildKit instance,
making several runner setup steps unnecessary:

- Rust toolchain installation (not needed for remote builds)
- QEMU setup (cross-platform emulation handled by BuildKit)
- All caching steps (Rust registry, cargo target, apt cache/lib)
- Cache injection step (BuildKit manages its own cache)
- Timelord timestamp caching (not needed with persistent build cache)

Also added output to git SHA and timestamp steps to show their values.

This should significantly reduce build time when using persistent BuildKit
by eliminating ~7 setup steps per matrix job.

.forgejo/workflows/release-image.yml

@@ -101,6 +101,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Install rust
+        if: ${{ env.BUILDKIT_ENDPOINT == '' }}
         id: rust-toolchain
         uses: ./.forgejo/actions/rust-toolchain
 
@@ -111,6 +112,7 @@ jobs:
           driver: ${{ env.BUILDKIT_ENDPOINT != '' && 'remote' || 'docker-container' }}
           endpoint: ${{ env.BUILDKIT_ENDPOINT || '' }}
       - name: Set up QEMU
+        if: ${{ env.BUILDKIT_ENDPOINT == '' }}
         uses: docker/setup-qemu-action@v3
       # Uses the `docker/login-action` action to log in to the Container registry registry using the account and password that will publish the packages. Once published, the packages are scoped to the account defined here.
       - name: Login to builtin registry
@@ -144,11 +146,13 @@ jobs:
         run: echo "TIMESTAMP=$(git log -1 --pretty=%ct)" >> $GITHUB_ENV
 
       - uses: ./.forgejo/actions/timelord
+        if: ${{ env.BUILDKIT_ENDPOINT == '' }}
         with:
           key: timelord-v0
           path: .
 
       - name: Cache Rust registry
+        if: ${{ env.BUILDKIT_ENDPOINT == '' }}
         uses: actions/cache@v3
         with:
           path: |
@@ -158,6 +162,7 @@ jobs:
             .cargo/registry/src
           key: rust-registry-image-${{hashFiles('**/Cargo.lock') }}
       - name: Cache cargo target
+        if: ${{ env.BUILDKIT_ENDPOINT == '' }}
         id: cache-cargo-target
         uses: actions/cache@v3
         with:
@@ -165,6 +170,7 @@ jobs:
             cargo-target-${{ matrix.target_cpu }}-${{ matrix.slug }}-${{ matrix.profile }}
           key: cargo-target-${{ matrix.target_cpu }}-${{ matrix.slug }}-${{ matrix.profile }}-${{hashFiles('**/Cargo.lock') }}-${{steps.rust-toolchain.outputs.rustc_version}}
       - name: Cache apt cache
+        if: ${{ env.BUILDKIT_ENDPOINT == '' }}
         id: cache-apt
         uses: actions/cache@v3
         with:
@@ -172,6 +178,7 @@ jobs:
             var-cache-apt-${{ matrix.slug }}
           key: var-cache-apt-${{ matrix.slug }}
       - name: Cache apt lib
+        if: ${{ env.BUILDKIT_ENDPOINT == '' }}
         id: cache-apt-lib
         uses: actions/cache@v3
         with:
@@ -179,6 +186,7 @@ jobs:
             var-lib-apt-${{ matrix.slug }}
           key: var-lib-apt-${{ matrix.slug }}
       - name: inject cache into docker
+        if: ${{ env.BUILDKIT_ENDPOINT == '' }}
         uses: https://github.com/reproducible-containers/buildkit-cache-dance@v3.3.0
         with:
           cache-map: |