t3032-*.sh: Do not strip CR from line-endings while grepping on MinGW

By default grep reads in text mode and converts CRLF into LF line
endings, which causes tests 4, 6 and 8 to fail. In a similar manner
to commit a94114a  (Do not strip CR when grepping HTTP headers,
2010-09-12), we set (and export) the GREP_OPTIONS variable to -U so
that grep will use binary mode.

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/t3032-merge-recursive-options.sh

@@ -14,6 +14,7 @@ test_description='merge-recursive options
 . ./test-lib.sh
 
 test_have_prereq SED_STRIPS_CR && SED_OPTIONS=-b
+test_have_prereq MINGW && export GREP_OPTIONS=-U
 
 test_expect_success 'setup' '
 	conflict_hunks () {