lib: source build replace the matching release

Instead of having an explicit vX.Y-dev version to be referenced
explicitly, a binary built from source replaces the matching
version. For instance, if forgejo/build-from-sources contains v9.0,

* the development branch is compiled from source
* the v9.0 artifact is uploaded
* prior to running any test, the artificat is downloaded and used
* the v9.0 binary is not downloaded from
  forgejo/experimental/integration because it is already present

The vX.Y release is built daily and the end-to-end tests run on it. If
a regression is introduced, it will be spotted within 24h.

Compiling from source is used when the Forgejo runs the end-to-end
suite on a specific pull request.

.forgejo/workflows/end-to-end.yml

@@ -31,8 +31,15 @@ jobs:
           go-version: "1.22"
       - name: lib/build.sh
         run: |
-          set -x
+          mkdir $d /tmp/forgejo-upload
+          touch /tmp/forgejo-upload/PLACEHOLDER
 
+          if ! test -f forgejo/build-from-sources; then
+             echo forgejo/build-from-sources is not present, do not build any version from source
+             exit 0
+          fi
+
+          set -x
           #
           # SQLite needs gcc to be compiled
           #
@@ -41,13 +48,12 @@ jobs:
           apt-get -q install -y -qq build-essential
 
           d=/tmp/forgejo-binaries
-          mkdir $d /tmp/forgejo-upload
 
-          for version in $(ls forgejo/sources) ; do
-            forgejo=$d/forgejo-$version-dev
+          for version in $(cat forgejo/build-from-sources) ; do
             lib/build.sh $version $d
+            forgejo=$d/forgejo-$version-dev
             $forgejo --version
-            mv $forgejo /tmp/forgejo-upload
+            mv $forgejo /tmp/forgejo-upload/forgejo-$version
           done
       - uses: actions/upload-artifact@v3
         with: