foreign_autotools: at_do_${i} does cd to HOME when ${_FOBJDIR} is blank

[ykaliuta]

triggered by tests/FSRCDIR

In the code:
at_do_${i}: .PHONY
${MESSAGE.autotools}
${_V} set -e;
cd ${_FOBJDIR};
if test -f Makefile; then
env ${AT_MAKE_ENV} ${AT_MAKE} ${AT_MAKEFLAGS} ${.TARGET:S/^at_do//:S/cleandir/distclean/};
fi
_FOBJDIR appeared to be blank the the following test operates in ${HOME} directory