Bake a selection of gradle versions into the image; use fdroid's gradle wrapper to determine which one to use.

Right now the image supports Gradle >= 3.0. This should be wide enough for the majority of use cases. If we need to add additional gradle versions we can easily do so.

entrypoint

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 REPO="$(pwd)"
-source /root/.sdkman/bin/sdkman-init.sh
+export PATH="/opt/gradle/bin:$PATH"
 
 if [ -d "fdroid" ]; then
     cp -Rv fdroid/* /fdroiddata/metadata;