tests/env/env.sh: Improve simple_echo

[oech3]

I'm not 100% sure. But

coreutils/tests/env/env.sh

Lines 23 to 26 in 0da738f

	# A simple shebang program to call "echo" from symlinks like "./-u" or "./--".
	echo "#!$abs_top_builddir/src/echo simple_echo" > simple_echo \
	|| framework_failure_
	chmod a+x simple_echo || framework_failure_

look invalid if echo is multi-call binary. Also abs_top_builddir does not work at externall usage ( AT_EXECFN based multi-call binary seems depending on individual echo binary).

[oech3]

Hmm, it might one of a reason why milti-call binary should not use AT_EXECFN...