More consistent gogs file construction

src/freedombone-app-gogs

         fi
     fi
 
-    GOGS_BIN="https://github.com/gogits/gogs/releases/download/v${GOGS_VERSION}/linux_${CURR_ARCH}.tar.gz"
+    GOGS_FILE=linux_${CURR_ARCH}.tar.gz
+    GOGS_BIN="https://github.com/gogits/gogs/releases/download/v${GOGS_VERSION}/${GOGS_FILE}"
 }
 
 function gogs_create_database {