BUILD: Fix building with automake 1.15
    
    The macro AC_BUILD_AUX_DIR was used too late. As a result of this automake 1.15
    generated configure script which ignored the directory build/ and was not able
    to find missing files.
    
        configure: error: cannot find install-sh, install.sh,
        or shtool in "." "./.." "./../..".
    
    After removing macro AC_BUILD_AUX_DIR, autoreconf will install auxiliary files
    into $srcdir.
    
    Signed-off-by: Lukas Slebodnik <lslebodn@redhat.com>
    Reviewed-by: Simo Sorce <simo@redhat.com>