t6038-*.sh: Pass the -b (--binary) option to sed on cygwin

The tests using the fuzz_conflict helper function (tests 5-6)
fail on cygwin in the same way they used to on MinGW, prior
to commit ca02ad3. The solution is also the same; passing the
-b (--binary) option to sed, using the SED_OPTIONS variable.
We introduce a new prerequisite SED_STRIPS_CR to use in the
conditional initialisation of SED_OPTIONS, rather than MINGW.
The new prerequisite is set in test-lib.sh for both MinGW and
Cygwin.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Acked-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t6038-merge-text-auto.sh

@@ -14,7 +14,7 @@ test_description='CRLF merge conflict across text=auto change
 
 . ./test-lib.sh
 
-test_have_prereq MINGW && SED_OPTIONS=-b
+test_have_prereq SED_STRIPS_CR && SED_OPTIONS=-b
 
 test_expect_success setup '
 	git config core.autocrlf false &&

t/test-lib.sh

@@ -1057,6 +1057,14 @@ case $(uname -s) in
 	# backslashes in pathspec are converted to '/'
 	# exec does not inherit the PID
 	test_set_prereq MINGW
+	test_set_prereq SED_STRIPS_CR
+	;;
+*CYGWIN*)
+	test_set_prereq POSIXPERM
+	test_set_prereq BSLASHPSPEC
+	test_set_prereq EXECKEEPSPID
+	test_set_prereq NOT_MINGW
+	test_set_prereq SED_STRIPS_CR
 	;;
 *)
 	test_set_prereq POSIXPERM