[spec] Allow to conditionally build without gradle
[spec] Allow to conditionally build without gradle

mizdebsk/xmvn,rvais/xmvn,fedora-java/xmvn,fedora-java/xmvn,rvais/xmvn,mizdebsk/xmvn,rvais/xmvn,fedora-java/xmvn,mizdebsk/xmvn,rvais/xmvn,mizdebsk/xmvn