Build: IPA_VERSION_IS_GIT_SNAPSHOT re-generates version number on RPM build
    
    This is a huge hack. rpms target will touch VERSION.m4 file. This change
    is then detected by automake Makefiles which subsequently re-execute configure
    and make.
    
    We have to workaround fact that variables in new make targets
    (executed after new configure) are different than original ones.
    
    Also, we have to 'bake-in' precise snapshot version from Git to
    VERSION.m4 inside of RPM tarball so the RPM does not depend on git
    anymore.
    
    All this magic slows build down a bit.
    Do not enable IPA_VERSION_IS_GIT_SNAPSHOT if you want fastest possible builds.
    
    The option IPA_VERSION_IS_GIT_SNAPSHOT is now enabled by default as it
    was before we started the build system refactoring effort.
    
    https://fedorahosted.org/freeipa/ticket/6418
    
    Reviewed-By: Tomas Krizek <tkrizek@redhat.com>