[bug-gnu-libiconv] check test error under cygwin

[baigali]

following piece of code not work as expected when make test:

the output into tmp-out is: B?0xc3??0xb6?se B?0xc3??0xbc?bchen

the expected is: B«0xc3»«0xb6»se B«0xc3»«0xbc»bchen

compare result: tmp-out tmp-ok differ: byte 2, line 1

iconv=../src/iconv_no_i18n
# Make sure the charset.alias file is found.
CHARSETALIASDIR=../lib
export CHARSETALIASDIR
options_ascii='--unicode-subst=<U+​%04X> --byte-subst=<0x%02x> --widechar-subst=<%08x>'
options_utf8='--unicode-subst=«U+%04X» --byte-subst=«0x%02x» --widechar-subst=«%08x»'
# Test of --byte-subst with a non-ASCII substitution.
if test "`(locale charmap) 2>/dev/null`" = UTF-8; then
cat > tmp-in <<\EOF
Böse Bübchen
EOF
$iconv $options_utf8 -f ASCII -t UTF-8 2>/dev/null < tmp-in > tmp-out
cat > tmp-ok <<\EOF
B«0xc3»«0xb6»se B«0xc3»«0xbc»bchen
EOF
cmp tmp-out tmp-ok
fi

is it a bug or a problem of my system? I am running on windows 10 under cygwin